I was lucky enough to be one of ther first people to get one of these amp heads, and I've been using it about a year.
This is one of the finest bass amplifiers money can buy. Hand-built by a genius in Poland, it's better than Mark Bass, better than Darkglass, better than Ampeg.
The Vandall 500 is a beast of a bass amp, it contains both a solid state and a valve preamp plus the ability to blend the two. You can go from gritty rock growl to clean Mark King pop and everything in between. It has a bass and treble boost and a sweepable mid that while increasing and decreasing the eq keeps the volume level. It doesn't saturate the tone of your bass, instead enhancing your axe rather than overpowering it. It also ways less than 6lbs, so it ahrdly breaks your back carrying between shows.
Last week, I had to use a friend's Ampeg SVT and 8x10 cab. I sounded dull and lifeless after a year with the Vandall.
Seriously. Get this.