Attached with this post is a whitepaper that contains a list of mobile broadband devices that are working on Windows 7 Release Candidate. This document also contains some workarounds for making your devices work on Windows 7.
Also included are some common steps you can follow to troubleshoot some of the issues that you may face with your mobile broadband device on Windows 7.
Hope you find this useful.
Devices Just Work, Mobile Broadband