I'm still learning but that's part of the fun. I am, as of right now, still using that UV but after what you've said I may take it off. I asked the camera shop guy the same thing, why put another piece of cheap glass in front of a fluorite lense element? It's bound to degrade the picture somewhat but his reply was something to do with the cost of repairing the front element.
I've got the 70-200 f/4L Image Stabilizer, 28-135 IS, and the 50mm f/1.4.
The body is a 40D, I got it in November last year, I had a 30D before but this was definately worth the upgrade plus I was able to recoup some of my expense by selling the 30D.
Thanks for your advice--Bran