I really should ban myself from going to guitar shops to try things. I've had GAS for a PRS Tremonti for months, but was holding off buying one because I couldn't get to the dealer to try it out (I'm in South Wales, only dealer who had one was in Derbyshire). Then World Guitars, in Stonehouse, Gloucestershire, which is only about an hour and a half's drive away, listed one in stock. Went up there today, tried it out for about an hour, and bought it.
It's a brand new one, built in March, with the new-type PRS birds on the neck, which I was unsure about from photos. However, IMO, they really suit this guitar, particularly in the gray black finish. The top is quite a tight flame, nicely bookmatched with vertical grain lines running at a right angle to the flames in some places.
I demo'd it through a Mesa Express 5:25, and the tone was astonishing. On the drive channel, it had thick, fat bass, clear mids and screaming highs from the bridge pickup, and smooth, chunky but still very clear tone from the neck pickup. On the clean channel, the definition on both pickups was astounding. It certainly doesn't seem to be a one-trick pony though. On a crunchy setting, there was a nice Angus-style snap and punch from the bridge, and a very satisfying bluesy tone from the neck. It doesn't sound like a trem-equipped guitar - it sounds almost as fat as the '77 LP Custom I was fortunate enough to play a few months back (not quite, but almost!).
Playability and setup was fantastic. Action, intonation etc were spot-on, and the neck profile (wide-thin) is a good compromise between a wide-fat, which is too chunky for me (I have relatively small hands) and very thin, Ibanez-style neck. I was also pleased to find it was strung with 10s, so I felt completely at home straightaway.
Given how good it was, it really was impossible for me to leave it in the shop. Here's a couple of quick pics (sorry about the quality, they're phone cam pics - didn't have time to break out the camera tonight)

On a related note, World Guitars is a really cool operation. It's run by the guy who owned Machinehead Music for years, and he's got some really interesting stock - Paul Reed Smiths, ESPs, Collings guitars and Mesa Cornell and Engl amps.
Apologies for the lengthy post, but it needed to be raved about!