I am loving my 8110, I am mobile, so need the GPS vs the Wifi, when I am home or at the office, I have wifi, and I have my laptop, being mobile on the BB is just that, mobile.
BIS has file size restrictions. For example, you can't download podcasts. You probably wouldn't want to do it on a BIS/EDGE data plan anyway. That would be awfully slow. That's where Wifi comes in.