Hi, I have just tried PianoBooster 0.6.1 with SimpleSynth and an external Midi device (in my case, it is a Casio Celviano AP45 digital piano), and I can report that it works perfectly. There is no noticeable lag that on my G5 iMac with a 0.99 Euro Midi-USB interface bought on EBay from Hong Kong ;)
