Indoor Event Photography

Hello all,
I know many of you do more than aviation photography, myself included, so I was hoping some of you Canon users could give me some help making some decisions. I have been asked increasingly about whether I do wedding/event photography for hire. I have done weddings, and do a pretty good job given that they aren't my specialty, but it has always been as a second photographer with their equipment, not mine - and with Nikon, not Canon.
I've been wanting to upgrade my wide-angle general purpose lens from the Canon 28-135IS to either the 24-105L/IS f/4 or the 24-70L f/2.8 and combine it with a 580EX II. I also am giving consideration to the 35Lf/1.4. I figure that if I'm going to start doing weddings/events work on my own more, I should probably favor my new lens choice to reflect what might be best for those situations.
So a few questions;
Does anyone use any of those lens/flash combinations for weddings/event photography? - if so, what do you think?

Any suggestions on whether I should go with f/4 IS or the f/2.8 without IS?

Any thoughts, especially from anyone who uses these combo's for this type of work, would be greatly appreciated.

spent sometime browsing at Canon USA...

i'd go with the F/4 IS...

the F/2.8 without IS seems like a choice, but I think IS would be important for a wedding..running, jumping around, etc...

The important thing to remember about IS is that it doesn't actually increase your shutter speed, it just lessens the effect of camera shake at low shutter speeds. What this means is that if you're shooting action in a low-light situation, you're more likely to end up with blurry pictures (because of the subject(s) moving) with the f/4 as opposed to the f/2.8.

I've never used the 24-105 f/4 IS myself but I've heard lots of good things about it; I have the 24-70 f/2.8 and it's quite possibly my favorite lens.

I would say that a fast prime or primes (like the 35 f/1.4) are probably the most important thing you could get; if you had a slightly wide prime and a slightly telephoto prime (50 f/1.4 (on a crop body) or 85 f/1.8) you'd probably be pretty well covered; you could supplement those with the 24-105 if you still had any money left over. If you only wanted to do one lens, though, I'd say the 24-70 f/2.8.

As for flash, it's always good to have one (or more) around but you'll definitely want to do some reading about how to get good results with it. Sticking it in the camera hotshoe and pointing it straight forward is not going to give nice results. Strobist is a great resource for learning about the basics of lighting and how to get nice lighting setups with only flash units like the 580 (as opposed to way more expensive pro lighting rigs).