[Vertigo]

...but navigation is extremely slow.

This video matches my experience. Plenty fast, IMO.

Thats fairly impressive, also considering its a build from September. Noticeably smoother than my openelec on (admittedly, very slow) sdcard.
I was about to install openelec on a USB HDD to see if that made a big difference. Throughput would be higher no doubt, but Id expect latency to be worse, so I wasnt sure it would be a big gain. For sure I wouldnt have thought a USB stick would make a big improvement over an SDcard as the author of that video claims though?

Anyway, now I may have to try raspbmc too .
And I took the liberty to link your video in the OP.