There are quite a number of programs that do not run on the Atari800Win Plus 4.0
There is a lot of room for improvement! The emulation is maybe 75%.
Example: playback of digital music files.
I have a collection of digitized music files that play back fine on any standard Atari 800XL. But no Atari 8-bit emulator can yet do this. (Why not??)
Games maximizing the Atari 8-bit's proprietary hardware in terms of graphics and sound so far are beyond the capabilities of any 8-bit emulator I've tried.
If there's anyone willing to work at making a better emulator, please let me know. I could help with money if that's what the obstacle is.
RE: How far can the Atari XL/XE be upgraded in 201