I'm a long time Trace Elliot user (AS400SM) and I use my own custom made cabs, which are very flat and "hi-fi".
I've just bought an Ashdown Routemaster 420 and here are a few observations after a week or so. The gain knob seems to need to be nearly maxxed out with my active basses. The compressor adds a lot of gain past 12 o'clock, which is odd because the manual says that the gain should stay constant through the compression. The Sub (octaver) doesn't have an on/off switch and it tracks pretty bad unless the compressor is engaged. The drive is ok, but there are better sounding op-amp based overdrives available. The 5 band EQ is very nice but I find that the amp seems to have a baked in "rock" eq which is a bit boomy on the bottom end. With this EQ, it's hard to dial in a truly flat eq. I like this amp's sound, but it does seem to have quite a dark sound at lower volume levels. As the volume (power section) gets pushed, the mids comes out more and the boomy bottom end seems to tighten up nicely.
In a comparison with my trusty Trace...sorry guys but my Trace does sound better, sounds louder for my 400w and also have a much more usable 7 band graphic eq. BUT...my Trace is a 25kg lead sled...and this new little 420w class D is only about 5kgs max. It's small and light...and it certainly sounds good enough for most gigs.