I just bought an album from the Ubuntu One album store. It was very quick and easy to buy but as with many things, once you have handed over the money it got alot worse. Basically the music was 'in my cloud' but it wouldn't sync to my local machine...
Ubuntu has
status page
Which linked to a
bug report
Which said to open Applicaitons->Accessories->Terminal and run:
touch ~/.ubuntuone/Purchased\ from\ Ubuntu\ One/placeholder; u1sdtool -q; u1sdtool -c
This will put a "placeholder" file in your ~/.ubuntuone/Purchased from Ubuntu One/ folder and then force the syncdaemon to reconnect and try to sync that folder.