I just received my Jerico Thumper a week ago, and I love it! The difference in power was noticeable right away, but I initially had problems with control. After a week of working with it, however, I'm making 2-3 balls on the break with an alarming (for my opponents) consistency, and I'm starting to squat the cue ball pretty good.
I'm still scratching in the side a little, because it's just sinking in that I can really just concentrate on hitting that one ball absolutely square--the power will take care of itself. But there have been a lot of little 3-packs going around the last couple of days. With this break cue, things aren't looking good for the opposition when I really start getting familiar with this thing over the next few weeks!
As for the jump portion of the cue, it's just tremendous! I was putting some extra practice with it last night, and I'm still getting accustomed to the vastly reduced amount of power necessary to jump with this cue! Because you can actually jump at just about lag speed, it enables a whole different level of accuracy and control compared to the dedicated jump cue that I used previously.
The tip holds chalk well and it can apply all the english that you would want for a break. I don't do jump masse shots, so I can't advise you on those, but for all other uses, I recommend the Jerico jump/break cues highly. My previous b/j was an old McDermott EB-6, so it's probably an unfair comparison. From what I've read, you certainly can't go wrong with a Varney or Predator, either. In fact, from what I've been reading on this forum it pretty much seems that once players give a Varney a crack, they might never go back!