Well it's here...
And I am very impressed. Instant classic Ashdown tone (if that's not your thing, this really isn't the amp for you), very warm (not muddy) but with plenty of grit and bite if you want it. Excellent drive control, despite the absence of any valves, and very reminiscent of my old ABM 500 but without the size and weight.
I've been using a Mibass for a while and really haven't got on with it - the comprehensive EQ and tone shaping isn't something I need and I found myself constantly twiddling the knobs and sliders. With the Rootmaster, it sounds great straight away, before the EQ is even adjusted.
It's heavier than the other lightweight amps I've owned (GK, Markbass, Ashdown) but it is a bit larger. I'm not even sure if it is in the same category as those, but it's certainly much lighter than the ABM.
So far I've only played it indoors but so far I'm really chuffed. I think Ashdown are on to a winner here, and I'm very happy.
Live test on Saturday!