THere are those rubber covers you can get for the 7100... there is a link somewhere. That would protect your screen and you wouldn't need a holster. I clip mine to my purse and it sits there all day.
My BB goes into sleep mode or whatever when its in its holster. THe backlight shuts off and it locks, so that I'm not accidentally dialing China while it's bouncing around in my bag. I know you can adjust this but I don't know where.
The best benefit about the 7100 series is that it is pocketable. As compared to the larger versions, you can slip it in your pocket or your bag, and it's not awkward and bulky.
You can surf the web on it but, in my honest opinion, it's slow and very extremely irritating. I live in the interenet and am more likely to just look something up at home, rather than look it up on the BB. Might do in a severe pinch, but its not preferable to using a pc.