I would buy, but that's just me. If you rent and there is an equipment change that your modem can't handle, you would get upgraded. If you owned it you would have to buy another.

I think there are some people that bought DOCSIS 1.0 modems and then AT&T switched to DOCSIS 1.1 and they got burned. I think there is a DOCSIS 2.0 standard coming out now too.