2012 Retina MBP. Upgraded and had some annoying issues. Tried clean install and, even though some issues got fixed, the worst ones were still there. Add that to major UI lag and performance issues and it was the worst experience I've ever had with any Apple OS. Got back to Mavericks and everything is great.
In the other hand I have two friends that upgraded their non Retina MBPs (older than mine) and reported no issues.
Personally, I won't upgrade for some time since I don't want to risk bumping into the same issues again and I'm counting on Apple to fix most of them but I guess that will take some time. Although I love how the OS looks, I'm not missing out on anything important. If you don't feel you need to upgrade, I'd advise you not to.