I've played 4 of 'em, all at LAG.
They are incredibly easy to play...incredibly comfortable. So much so that one 6-string was in the running against the Jerzy Drozd I ended up buying from Dan.
Vadim puts a ton of effort into building basses that have multiple laminates, interesting shapes, carved tops, wooden cavity covers and pickup covers, etc. The tones he coaxes out of these woods is amazing!
There is a downside, though not much of one. His work is done by hand...entirely. You can tell. He's really meticulous when it counts, but some of the routings look like he had a worn-out jig.
That said, IMO, his work is good enough to look past the minor (and I mean minor) cosmetic flaws. His fretless bass was so "mwah-y" and growly I couldn't believe it...and, according to Dan, when he told Vadim how "mwah-y" it was, Vadim replied, "...that ain't nothin'...if you want mwah, wait 'til you see what I can do!" I haven't seen another fretless of his, but that one was unreal.
