I want to get these games, but I hear the early ones in particular are a pain to get running on modern OS's. Is Soul Reaver one of the games GoG only kinda has Win7 support for, or does it play well?

For the most part the games have been patched and tweaked to install and run on Windows 7. I had to do very little other than adjust a compat mode to get the games all running really well, nearly flawless for me. They run without issue for me personally and I'm on windows 7 64bit ultimate.

There are a small group of people that have had some issues with major sound or flickering issues, it just seems that some hardware setups the games don't run well with.

The games are as patched up as they will ever be though. They are more likely to work for you than not.