I shoot events and you very much want E-TTL when you are doing so. There is a time to fiddle for max quality, events usually will not let you do that. There is a reason why PJs shoot run-and-gun style, relying on automation to help them get the shot. All the best composition, artistic framing and whatnot goes out the door when you miss that key moment that is gone in the blink of an eye before you can even reach for the shutter button.
I second Curtis' recommendation of a flash. I have shot many, many events and only recently just 'arrived'. I shot in some of the worst possible light one could ask for (1/5 sec ISO 1600 f/4) with a slow f/5.6 zoom (just to show myself it could be done). Proper use of the flash will allow you to blend ambient and flash light for incredible results at incredibly low shutter speeds in horribly dim light at some evening events.
Some of the photogs shooting alongside me are college/uni folks who are on entry level 350Ds with kit lenses, but their mastery of the equipment and their talent shows. Almost makes me feel bad to break out the 5D and 24-105.
You can get stunning results with the 350D/18-55 together with a flash. Flash is a tremendously simple device to use (just point and shoot with ETTL) but tremendously difficult to master. Most people give up and go back to 'available light only'. I've made that excuse before - because I was too afraid of the flash! So I know what it's like to say it. But I also appreciate the challenge because it is like trying to control two separate exposure devices simultaneously, one of whose effects you CANNOT see through the viewfinder and must visualize in your mind.
That having been said, I suggest the 430EX. Many go straight to the 580EX but I have never felt the need even in the worst of conditions. Don't be overwhelmed - feel free to shoot in full auto, but do take the time to learn and master it. Many of the flash secrets are the ones that are not immediately obvious.
Also, search POTN for the Emergency Bounce Card (EBC). Far from 'emergency', I routinely used the EBC because I didn't need to rubber band anything to my flash. It's cheap, cheerful, and easily obtained.. it should be a staple in any 430EX user's arsenal. My bag has half a dozen in case I need to use or share them with fellow photogs. I recently switched to the Joe Demb Flipit and I love it, but the EBC is still a staple in the bag just in case I forget the flipit. Of all the diffusers I have ever used, I prefer the old school bounce card in all of its various incarnations (index card, folded paper, rubber banded to the flash, EBC or Flipit - in order of technological sophistication
)