Garbage. Parallels crashed when attempting to run non-demanding applications through a Windows 8.1 VM. Every subsequent attempt to restart the VM would crash Parallels again during the startup process. Parallels support is beyond useless.
Switched to VMWare Fusion 7 and all has been right with the world.
If I was to try VMWare Fusion 7 how could I move over the games etc I have installed under Win 7 in Parallels ? Just so to save re installing it all.
Works good for me, but I don't run games. I use it for test installations of previous OS X and Linux versions, and use several Windows applications under XP, 7.1 and 8.1.
The time I save by not rebooting to run other OSes native easily offsets the minor hit in performance my usage sees.
I don't think I've had a problem at all with version 10 except the handling of hidden docks on guest OS X vs. host OS X. VirtualBox does it perfectly, P10 works easier if one isn't hidden.