They seem to be very easy to drive and are quite efficient (cf. HD-650s), and have excellent bass. I was brought up on Linn Saras and Isobariks, and latterly Shahinian Arcs, all of which produce proper bass if you drive them correctly, i.e. lots of punch, but no bloat.
Regarding the DAC, I'm very happy with it, compared to my LP12/Lingo/Ekos/Dynavector DV17 and Densen B400. The V1 is smooth and dynamic and definitely has the Naim trademark sense of rhythm, to the point that I'm not sure the Densen is worth keeping; and the B400 does rhythm very well. It was the first CD player I heard that didn't sound appalling after the LP12. But that was a while ago, and DAC technology moves on.
The V1 stomps all over my Arcam DV88, and original CypherLabs Algorythm Solo (which in turn stomps all over my old iPod with Wolfson DAC). And all of the many other digital sources I've ever heard but don't own, including the Naim CDX-2 (which was one of the better ones, but not as good as the Densen).
If you haven't yet checked out Jude's recent Winter 2013 guide, he described the DAC section of the V1 as "awesome", and he seems to have heard or owned just about everything that gets discussed around here.