The one I had was pretty wavy when the head was at the top of the column, but other than that, it was fine.
One quirk with these (and Focomats) is that the bottom surface of the condenser is in contact with the neg, so they can easily get dirty and dusty. Pretty common to find cleaning marks or scratches on the condenser - bring a good pocket flashlight to carefully inspect the condenser when you buy, and don't buy sight-unseen.
This condenser arrangement also means the Valloys are prone to producing Newtons rings
. If the enlarger you are considering has what appears to be a press-on frosted glass filter covering the bottom of the condenser - then it has the Leitz anti-newton-ring glass (worth at least 3~4 times as much as the Valloy), and you don't have to worry about this (It's unlikely that a shop specializing in Valloys would let one of these slip by unnoticed)
I believe some 50mm enlarging lenses need a 1cm extension to work with the Valloy (or is that only a factor with the Focomat?).
However, I don't understand why you wouldn't want an MF enlarger, an Omega B-22
or a Durst
; both of which are close to your size/weight requirements, built like tanks, and would also allow you to enlarge M.F. negs as well.