Picked up an i5 XPS 15 in the last couple of weeks from Dell Outlet and I've been very impressed so far, although I've only got the standard 768p screen.
As mentioned the sound is about as good as you can get on a laptop at the moment, still limited on the bass but nice and bright and doesn't distort too much even at full blast.
The keyboard is a bit spongey but adequate (no backlighting on the UK models), the touchpad is nice to use and configurable to the full range of gestures which is a nice feature.
The nv gfx is pretty good for the price and adequate for running most current stuff at medium. Gets a bit toasty when its running games and the system fan will get fairly loud but not too bad. NV's optimus tech switches seamlessly between the nv and on-chip intel gfx very well, had no problem with it. Normal use, the system fan spins up now and again if turbo-boost kicks in but mostly it stays very quiet with the cpu fan just about audible.
The standard 6 cell battery is ok but you'll be lucky to get more than 2 hours out of it if you're running a lot of multimedia flat out, more like 3.5 if you're just surfing. If you can get one with a 9 cell it's obviously better but the battery is a lot bigger and will raise the base quite a bit at the back.
Slight draw back is the weight, it's a pretty bulky unit so if you were planning to carry it around all day you might find it a bit cumbersome. Also, the third party usb 3 tends to drop out a little too regularly, seems to be connected with power management, I'm trying the latest drivers so I can't say as yet if it has cured the problem, hope so as it's a major pain if you're using a wireless mouse.
All-in-all for what I paid (£430) I'd consider it a bargain, so if you can get one for this sort of price you can't go wrong really.