8.1 (Sadly) introduced a lot of issues for me. I upgraded both home and work PC's to 8.1. I haven't tested my home PC's for compatibility yet. My work PC though... sheesh. Visual Studio 2012 seems to consume just a little bit more time when performing any operation. My SQL Server Management Studio is just about worthless at this point. I cannot register with any of my servers and cannot get status on any SQL server agents. I have to RDP into servers to run certain queries now or perform db maintenance.
Of course there would have been some unforeseen issues, but this is disappointing.
Interestingly... AFTER you install 8.1, there is a notification about downgrading. If you no longer want Windows 8.1, you cannot go back to 8. The downgrade path is to 7. Period.