The best upgrade yet by a long margin. (Yes I know the last version with an improved GUI was a great release, but that was really just a preview of this one!
I know many upgrades in the past have fixed game compatability issues, and actual emulation bugs which a lot of people here would consider more important that "cosmetic" changes.
But for me this is the best simply because the whole appearance and ease of use of WinUAE has changed for the better. The first thing I remember about WinUAE is how much trouble it is for a newbie to get an acceptable looking screen. With this new version, it runs and looks OK in windowed mode "straight out of the box". This is only gonna encourage more people to try out this program (and to stick with it) which is why I rate it so highly.
On top of this all the changes such as the quick start configuarations make a newbie who has never used WinUAE (and possible an Amiga) before not be spending their time scratching their heads when they could be falling in love with the Amiga (again).
Thanks for the great work Toni, roll on the first non-beta