It might make sense to target eBay users for digital music sales, as many of the sales on eBay are music related, except that most are look either for cheap second hand CDs or fan more likely deleted unavailable and rare CDs.
GetMusic has neither of these.
eBay users also tend to be the kind of people who want CDs, not digital downloads.
Personally I buy music on eBay specifically because I couldn't get it anywhere else. Both of Primary's CDs, Armoured Angel, old singles. If I didn't already have all of The Sharp's CDs (except the darn Xmas tape) I'd be buying them from eBay. Because you can't get them anywhere else. Not even iTunes.
GetMusic is at least getting a few things right. The songs are cheaper than iTunes, in MP3 format and at 256kbps. You can also sign up as a "fan" of an artist and be informed when new releases are available.
That would be awesome... except that I just went and looked up Tori Amos and they don't have her new album up yet.
Useless.
They're also Australia only.