Annoyingly, I've bought one of these just before the form factor changes and it becomes a nice square board.
Up and running immediately out of the box, which is nice.
The kernel supplied on NAND flash is recent enough that it supports CONFIG_FHANDLE which is needed for the upgrade to Jessie.
The instructions for Jessie upgrade are straightforward and appear to be working correctly: they also suggest apt-get autoremove and apt-get autoclean to clean up which is a very nice touch.
The sources.list in apt was already pointing to my country's Debian mirror which was even nicer.
Quite a good experience immediately from unboxing: it also adds to the number of machine architectures I've run Debian on:
alpha, amd64, arm, armel, armhf, i386, sparc - not bad for a start.
It's a bit slow - but it's a SoC, so what can you expect? The PowerVR graphics demos were spectacular but the drivers are very definitely non-free - you can't have everything.
[I do notice that there is an FSF-friendly Debian variant, though not yet certified as such - presumably not including PowerVR drivers]
(Lots of occurrences of the word "nice" in this post that I've just noticed. It's either understatement or just that I'm British)