Pros: Superb SQ, bomb-proof build, small and compact
Cons: The UI is a little awkward, but you get used to it
Simply stunning sound quality - will drive anything with its massive power output.
The UI isn't brilliant, but it is OK. English instructions would probably help (maybe I'll write some).
Head and shoulders above the Sansa Clip+, but then so it should be at 10 times the price.
Update - 5th October 2012
I have had this player for the best part of a month now and still love it to bits. I recently spent a week on a beach listening to this player and have to say that it lasted all week on a single charge with still 50% left for the plane home.
What impresses me most is the detail and clarity that this little unit squeezes out of every track I've played on it. I listen almost exclusively to Pink Floyd and Roger Waters' material (all in flac) currently through Etymotic HF5s (which may be a little too clinical for use with the Studio), although I am seriously considering some CIEMs to go with this high end PMP.
I have heard detail and layering that I didn't even know existed in some of Waters' albums. I've compared a number of tracks with the Sansa Clip+ and it just doesn't pick up some of the background samples and voices like the Studio does.
What I will say is that this player will show up any poor quality recording or compression, so aim for the best quality formats you can and you'll be fine.
I am still finding the UI a bit clunky, but I am getting used to it. Also, there is sometimes a very slight click between tracks on albums where one track leads into the next (ie most Pink Floyd albums !). Whilst this is not enough to not recommend this player, it would be nicer if it wasn't there. I have not tried any other firmware with this player as I love the sound that comes as standard.
In all - highly recommended if SQ is your bag. Everyone at work who has plugged they (rubbish) iPhone earbuds into it have been impressed *sigh*. If it can make them sound good, just imagine what a decent pair of IEMs will sound like ;-)