I've not sent a fax from my machine since I converted to Win 7, but I did find that Windows Fax & Scan can't see my scanner. Everything else can. It's a pretty conventional USB scanner, running through Twain. But no way will W F&S see it. I can faff around with Paint Shop Pro and printing to the fax, but that shouldn't be needed.
Apart from that, I'm impressed. The only annoying bit is all the stuff I've installed and set up that I'll have to do all over again when the DVDs arrive from Mr MS in a few weeks' time.