Ok, got an eTrex 30, Basecamp Version 3.3.2.0 on a Mac OS X 10.6.6 and bought some Birdseye Select credits (as an aside Basecamp doesn't show how many credits I've got - always a 'blank' when attempting to present... "you have [ ] of unused credit for this product" etc). I digress...
I've tried two different UK map areas and even a tiny area and everytime I get "Basecamp could not complete the download of this imagery. You may retry the download of missing portions of this imagery" (which doesn't then work either). Google searches suggest Garmin Basecamp servers might be experiencing problems but I tried last night and again this morning. Am I doing something wrong or is this just broken?
Pretty disappointing first experience of the "eTrex 30 also supports BirdsEye™ Select map download service that lets you download premium raster maps to your device and integrate them with your existing maps" - it ain't happening.