The major features:
-USB OTG(connect hds,mouses,modems,keyboards,prints)
-it can run debian,ubuntu,arch linux, mer,meego,nitdroid(gingerbread),windows 98
-high customizable if you know what youre doing
-hardware documented
-watch and download youtube videos
-tv output,gps,5mp with manual controls,raw format,led and autofocus,fm receiver and transmiter,audio stereo,qwerty,mobile modem,bluetooth tethering
everything in c++ and qt without loss too much performance in ram and cpu like android and its java virtual machine

but i dont understand whats the problem with the "new" n900 from ebay?(it has fragile hardware,its old and used)