For run and gun the kit lenses are fine. I have them both - the 18-55 and 55-200. The image stabilization is a lifesaver. For handheld video it's a must-have for any lens longer than about 35mm.
The main thing a better lens will get you is speed (wider apertures). But that gives you even shallower DoF which is what you need to avoid in run and gun.
One last thing- on Canon DSLRs it's important to use only ISOs divisible by 160. All the others give you lots of extra noise. Google this for details. A program called Magic Lantern can help with this if you want to dive in to such. Good luck!
Joe
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Joe Shapiro
Director / Freelance FCP Editor
206-420-6411
http://www.imdb.com/name/nm1497731/
http://JoeShapiro.com
http://en.wikipedia.org/wiki/Zoo_(film)
http://NWFilmForum.org/PoliceBeat
