I'd say around 90%.
Certainly good enough for playing games and general Amiga fun.
The biggest problem (and its no big deal) Ive noticed seems to be with screenmode handling.
I find the emulated screen doesnt fill my PC screen correctly. Its either missing part or bordered with black which has occasional garbage flickering on and off.
Im not sure if this is just a simple, tweakable, settings problem or down to the differences in Amiga/PC screenmodes?
Is there something like a stretch-to-fit setting in recent WinUAE versions?