I played with it. I didn’t care for the UI, which was very un-Mac-like and looked like it might’ve resulted from porting the app from another platform. I also found the latency to be pretty poor (this is with a Santa Rosa MacBook Pro and an M-Audio MobilePre USB audio interface). I tried playing with some of the settings like the size of the playback buffers, but to no avail.
Since I already own Logic Express, I gave up rather quickly on XO Wave and used Logic Express, with much better results.