I have an 810, a Motorola V3xx, and ATT's $20 Media Max plan. The V3xx teathers via bluetooth to both the 810 and my Powerbook. The parameters I used for the 810 might be useful to someone:

CONNECTION NAME: AT&T Internet
CONNECTION TYPE: GPRS
ACCESS POINT NAME : wap.cingular
USER NAME : WAP@CINGULARGPRS.COM
PASSWORD: CINGULAR1
DIAL-UP NUMBER: *99***1#

Good luck!