I took a chance without being sure and purchased a SanDisk 4GB Micro SD card for my T-Mo 8800. It works fine. I got a bit worried since I kept getting a message about mass storage and non compatible content every time I hooked up to my computer, but that could be turned off in the settings.
I also want to get as much music as possible on there and have found that Windows Media 10 Pro at 64 mbps (not wmp9!) is equal to mp3 at 128 mbps, and better than AAC at the same bitrate. This is my (and some firends and family's) ears talking or listening rather, so please take the statement for what it is.
What is really great is that I can create 2 pass vbr files and they play on the BB (give them that little extra crispness). Using dbPowerAmp to convert wav's from my CD's has resulted in great sounding sub 2 mb songs to go on my BB, all 1,600 of them actually!
So now I hook my BB up to my home stereo and think: All this from a phone!
P.S. Who came up with the idea to engage Sonic in creating the media manager for the BB's? If you want lower bitrate files it doesn't even transfer tags and cover art which the BB player nicely displays. Oh well, dragging files on to the BB from Explorer works fine, so who needs the Sonic stuff anyway?