Naw, I have no need for Musepack. I encode almost exclusively to vorbis and flac. I see no real need to mess around with new formats when these two do the job just fine. I do have one downloaded album in .mpc format, but I got tired of the incompatibility issues I kept experiencing with the files (in particular a bizarre problem with accessing them over my nfs share), and converted them to .ogg format for regular use.
Frankly, I wish the computing world would just hurry up and settle on one or two decent open-standard multimedia formats, and quit throwing us all these different attempts to reinvent the wheel.
But to each his own, I guess.