I was rather surprised at how loose and undefined both Herberts I played were without a boost. One I owned for about a month and a half or so, and the other I played quite extensively on several occasions in a local store with my cab and guitar. IDK, maybe both had tubes that were on the beat side or some other issue, but I think the odds of both having something wrong were pretty slim. They are however quite high wattage heads and maybe they needed to be cranked up to small arena volumes before they tightened up on their own.
Boosted they tightened up to a really sweet spot. Tight enough but still had some sag/forgiveness that made them a real joy to play. Man that amp felt fucking good under the fingers. I could be wrong, but thats kinda what I expect the Uber to feel like.