I made the jump without too much trouble.
First, it didn't take me too long to realize that there is the Windows 8 app world, and the familiar desktop interface. Once you realize the desktop itself is kind of a Windows 8 app/tile, it isn't too hard to get acquainted with it.
I had a problem initially with none of the windows 8 apps working for me, but that was because my avast antivirus needed to be updated first.
I haven't really found any of the stock windows 8 apps that appealing to me. Except for gmail, none of my email addresses can be recognized with the mail app, and the photos and music apps don't work for me at all because they don't support my media being on network drives, even if I used the mklink trick to create symbolic links to the data in their respective libraries. I'm told that new Windows 8 users can get a free copy of Windows Media Center (normally $9.99), so I might try that and see what it looks like, otherwise, I'll stick with Media Monkey as a desktop app.
I don't think some of my offsite backscript scripts (created with Winscp) are automated anymore, but that's probably due to a missing or moved key.
Didn't have any problem with Putty. Haven't tried Eclipse yet, but I don't expect any problems with that, running in the desktop space.
It would be nice to be able to replace more desktop apps with Windows 8 apps but there aren't really that many that can be at the moment.
Overall, the new interface isn't too bad, it's no worse than any other UI, at least from the first 8 hours into it.