I've been using Windows 7 at home since the public beta came out in January, followed by RC1. I recently transitioned two of my home PCs to the retail Windows 7 Home Premium a couple weekends ago. I made the transition on my workstation at work last week.
So far I'm very pleased with the transition, and I haven't had any major issues. A few applications had issues installing explorer context menus, but that wasn't a perfect situation even on XP 64-bit, and I've mostly sorted it out at this point. Every Windows 7 machine I currently use is a 64-bit install. For the last year I've been 64-bit (XP) on my work machine, so I am already familiar with any platform differences there.
UAC doesn't bother me - I'll most likely dial up the setting a bit, as the default isn't strong enough protection.
One thing that currently gets me is I can open my.ini (MySQL configuration file) in notepad (from explorer), but then I don't have permission to save the file once I edit it. It would be nice if it prompted me, instead of just failing. I do not see a right click menu option for "open as admin", but running notepad from an admin console solves the problem.
I tried "Windows XP Mode" for the first time today at work (it being Professional - which is a requirement). I was unimpressed with the performance of the installation of our app (4GB install and tens of thousands of files), but the actual execution speed of running applications in it was fine. I'll probably use it occasionally, but I don't think there are a whole lot of cases where I will need it.
What transition issues are people hitting? I'm curious how many people are trying it, and more curious when business roll outs will start in earnest.