PLEASE get with the need for multiple monitor support. Specifically: Multiple taskbar support! Span AND Extension on 3 monitors as a basic option within the "display" section

You could try the "Send Feedback" link at the top of any window in the Beta build, although it'll will most likely be to late in the day for that now. Windows 8 maybe? ;-) Please Propose as Answer if appropriate

Additionally, you can post your request to the "Have Comments about Windows 7 Beta (part2)" thread. Suggestions posted there are collected and forwarded to the development team periodically.