My experience with AllOfMP3 is generally good, except with what you mentioned: they seem to be victims of their own success and 'server busy' messages are quite frequent during some parts of day. However, once you manage to "order" your music, downloading (using their pretty good download manager) goes smoothly.
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Dragi "Bonzi" Raos Q#5196 MkII #080000376, 18GB green MkIIa #040103247, 60GB blue