jscomposer
I use a ton of EastWest instruments, and I'm still on Play 3 because it works perfectly. Do you notice any improvements with Play 4? Great to hear it works in X3!
I probably wouldn't get 4 then most likely. EastWest is not great at the programming. For me, it does work better since Play 3 had pops and clicks in bounces, which I couldn't get rid of. Play 4 has other problems, as I noted, but they can be worked around. However if Play 3 works, stick with it.
The improvements in Play 4 in general are it has a nice mixer interface, if you use multiple instruments in one instance of Play, the mixer is a good one. Also it has support for the SSL plugins, if you pay EW for them. Of course Sonar emulates most of the SSL stuff, like the compressor, very well so how useful it is in Play is questionable. Also they jettisoned QT and did native graphics which should have less compatibility problems with VE Pro.
I would say "Ya upgrade" if EW wasn't so problematic. Since it is, if you are 100% happy then stick with it for now.