I have a very well configured and smooth operating S1 3.5 pro which does everything I want it too and very well, with LOTS of features not even yet explored. But to get it working this way i had to back rev 1 version on the driver for my interface (Tascam us1200) the current driver would lock the audio engine. I am curious about the new Drum Generater in 4 but dont want to uninstall 3.5 pro to run 4 artist.I cant Imagine it being a better option than EZ Drummer 2. Can the two versions Of S1 run and exist on one computer ?(i think i already know the answer) It took me some time to figure out and get my system all working well. (My Core setup is a DELL 8200xps, Faderport 8. S1pro3.5, Tascam US1200, Akai LPD 8, Toontrack EZ Drummer 2 And a collection of outboard Mic pre's, Mic's, and Guitar/Bass Modelers/Amps ) I am am an experienced DAW user and know all to well the headaches possible in upgrades and changes to the core setup and dont want to lose or sacrifice anything just to satisfy my curiosity