I know this is a very old post, but I've been using MP3 for years for uploading/downloading, and I've never had any problems with syncing in a DAW, that's why I use Cakewalk Sonar X3 PE, for some reason, I think it converts the MP3 back in to wav, granted, music producers would prefer raw WAV, and so do I for uploading seps, or for mixing seps, but for general mixdowns I always use MP3, as long as I keep the sample rate at 44100Hz, and the bit rate as 32 bit, and using all defaults for the MP3 conversion, I don't hear any difference between MP3 or WAV, the only visual, difference is the file size. For uploading, MP3 is much faster, and many times I've tried WAV and even though the file size can be quite large for a 3-4 minute song, uploading large files can be and are subject to transfer errors, and failed uploads, hence the need to use MP3 for uploading.