Your choice of camera modes depends on your goals.
For me, getting a correct exposure while keeping up with quickly-changing scenes is paramount. That is, I do not want to sacrifice
either moments or exposures. Correct exposure or get the shot? False choice, I want
both.
For that reason, I only shoot manual. When shooting in any automatic mode, you have to be constantly fiddling with camera settings (the auto-exposure compensation) as a scene changes in order to get a correct exposure.
With manual, it's easily possible to get both correct exposures and not miss a moment, whereas with automatic modes, you frequently have to choose one or the other, and if you're going for a correct exposure, you're probably going to miss the moment.
Some of you are now saying, "Hold on Radlinski. You're telling me I'm going to
miss shots because I'm using an automatic mode?! That's crazy talk! I shoot automatic so I
don't miss shots!" Which is why your exposures are probably inconsistent, especially as a wedding photographer dealing with so many contrasty subjects, like white dresses and black tuxes.
We recently had a lengthy discussion about the way your in-camera meter works in
Lauren's thread. You might want to read my description of how reflective meters (like the one in your camera) work before reading further.
The problem with any automatic mode is the same problem Lauren had. All that automatic mode is doing is lining up that exposure needle in the middle of the indicator, and that's what it's setting your camera to. So, unless every scene you're shooting is 18% gray...all your exposures are going to be off! Obviously some will be more off than others.

Point is, now you're having to change your camera setting every time the scene changes! And since the scene is going to change image to image, all your exposures are going to be off.
Now if you're shooting in a manual mode, you don't have to worry about the scene changing...only the light changing. And usually the light doesn't change much between shots. Or it changes in fairly predictable ways. But the scene you're photographing can change drastically, as, say, you go from shooting a close-up dress detail (very white scene) to an overall picture of the room the bride is getting ready in (probably average gray scene). Light didn't change...but the scene did, and therefore the correctness of the camera's assumption of "18% grayness" did.
So what do you do to get a correct exposure in an automatic mode? Well...you have to use the autoexposure compensation button on your camera (or the exposure lock after finding a gray scene, like a gray card. No one does that, though) However, then you're just basically doing the same thing you would be doing if you shot manual, only now you're having to massage that dial every time the scene changes, instead of every time the light changes!
Photographers are visual people, so, for your enjoyment, pictures:
First, this is what happens when I use manual exposure modes but don't understand how the reflective meter in my camera works. This is a picture of the white light switch on the white wall behind my computer chair.

All I did was put the indicator in the middle of the exposure guide and clicked the button. That camera meter told me 1/500 at f/2.0. Of course, this is wrong. The camera meter is assuming the scene it's looking at is 18% gray. Since it's almost pure white, the meter reading is off by two stops. Looks 18% gray now, doesn't it? (Further reading:
Zone System)
Thankfully I'm a clever guy, and know how to compensate for the flawed assumptions on which my camera meter is operating. If I want this scene to be exposed correctly, I know I need to set the camera so the needle lands 2 1/3 stops over the center reading, since it's almost a pure white scene. Pretty far off from 18% gray. So instead, here's the scene at 1/100, f/2.0:

Much better, eh? White switch, white wall...looks good. And you know what else is great? Now that I have a correct setting on my camera, I can point it at anything else in my office that's lit by the same light and just...press the button. I don't have to fumble with any camera settings to get a correct exposure. That makes sure I won't miss this...awesome shot of my red swingline stapler!

Exact same camera settings as the previous image. Check the EXIF data if you don't believe me

So look at that...great exposures, no camera gymnastics, no missed moments.
Okay, so that's what's awesome about manual. Now let's look at how the program mode utterly, utterly fails, and hurts my soul.
By the way, no lie, I had to bust out the instruction manual to my 1D Mark 3 to figure out that there was no "full auto" mode on the Mk3. This was, for-real, the only time in my entire life I have ever used an SLR camera on any mode besides manual. Seriously, these few frames I shot for you guys are
it. I feel kind of dirty now, actually...and not in the good way.
Anyway, first, let's switch to P mode and point it at that light switch again.

Oh, shocking, massive amounts of failure. All it's doing is buying into the same false assumption as the reflective meter in the camera...that the scene it's looking at is 18% gray. So, it gives me the same wrong image as when I incorrectly used the manual metering mode.
So what do you do to get a correct exposure using this automatic mode? Well, I jack the autoexposure compensation up by 2 1/3 stops and take the image again. Kinda of like what I did in manual mode, only more difficult (have to press a button instead of just spinning a dial, in P-mode anyway) and time-consuming (since I have to do it on a scene-by-scene basis instead of a light-by-light basis)

Well that worked.
But oh, man did you see what that stapler was doing! It was CRAY-ZAY!! Better get that shot!

Oh, whoops. I didn't have time to hit that AEC button and dial it back down to "no compensation" for this generally-average scene. So now it's about 1 2/3 stops overexposed. Hope that awesome stapler action wasn't important to my client!
Let's dial that down now and take the shot again...

Eh. Now it's still about 2/3 stop underexposed, since the camera's assumption still isn't right. This is a scene that's about 2/3 a stop "more white" than 18% gray. So I had to fiddle with the camera quickly,
just from changing the scene, not the light and still got an off exposure.
So what's the moral of the story? Photography is all about light. I've said it I think five times on this forum in my 180 or so posts, that the analogy that photographers are artists who use a camera instead of a brush is false. We as photographers are artists who use
light instead of a brush. Photography is all about light, so if you're going to fiddle with camera settings, do it because of
light, not because of
scene.
If you use manual exposure, you can get perfect exposures without missing shots with minimal camera gymnastics. If you use any kind of autoexposure, you're either going to miss shots because you were playing with the AEC to get a good exposure, or you're going to miss exposures because you were so focused on the shot that you didn't have time to play with the AEC.
If you don't care if you miss one or the other, please continue to use automatic settings. But as a professional photographer being paid thousands of dollars (or in half-eaten sandwiches...depends on how bad the economy gets

) to capture images (and capture them correctly) for clients, I would rather get both.
Cheers,
Matt
P.S. Oh, and if you want to try this experiment for yourself, remember that the color temperature of the light in the scene can effect your exposures. For this, I turned the Ott light I use for color comparisons onto the wall, so I wouldn't have to worry about the tungsten light in the room screwing with the color-correct exposure by saturating the red (and green) channels at the expense of the blue one. If you don't have an Ott light, perform this experiment in daylight, just for control purposes.