For some reason, I don't think I have found one single program that have had a problem with Win7.

Maybe the Keil tools could have had problems - I was a bit late with upgrading them.

I run Win7 64-bit both at home and at the office and have done for a very long time. I was very scared about potential problems going 64-bit but have been happy with the choice.

The only hw-related problem I have had is a no-name serial-port board I bought. I suspect that it was the reason for a couple of reboots and video graphics restarts I had maybe once/month - always at times when I pushed large amounts of data through the serial ports. After maybe 6 months, the serial board died permanently, and after that the computer have worked perfectly. Serial data through port on motherboard or USB-connected dongles have not been a problem. Just serial data through the two ports on that board.

I also run VMware with a lot of emulated machines and normally a very large number of programs running concurrently.

The biggest problem with compatibility came may years ago - all the tools that expected direct memory access in Win95 and Win98. So I have some old PC with Win98 for some old programmers etc.