Works beautifully for me...
It's got a linux upload client, which is something neither Amazon nor iTunes can supply.
It uploaded about 15,000 tracks in a day or so. It converted all my .flacs to 320K mp3 (bar four, for some reason). I have a few albums which are a single .flac + a cue list - that just appeared as a single track. Would like to see that work better.
It skipped over all the .wma (but I only have a few of those).
It found a few tagging errors which caused tracks in a single album to appear split across two identically named albums - but you can fix those easily.
And I can now stream ALL my music to my phone wherever I am - and it's now backed up on the cloud.