Same for me, use it in a VM, etc. I've been doing this since 18 and have found it to be very stable. My only complaint would be Fedora 21 seemed like the filesystem was a bit slow. But I yum update pretty regularly and it seems good now. This is all anecdotal, just noticing startup times of the product I work on and other programs I use daily.

EDIT: I just remembered something important about my use and might be why that you say it wasn't good before 19. I use MATE mostly because 18's Gnome3 was really bad. I still don't like Gnome3 and stick with MATE. Gnome3 is just too slow for me and some of the workflows get in my way.