I actually do think Rebuild is quite a bit like Jack. It's a very strong baseline which more than anything is very very resilient, and quite a bit weaker in colony games. Jack is one of the strongest few 4s, and Rebuild is stronger. Of course, it costs more, which isn't so much a problem, except that there's more of an opportunity cost. The best way to beat either one is to be faster.
I played Jack against Rebuild a few days ago and won, well I felt relatively comfortable, but it was reasonably close. Note that actually on the same board, they don't work so terribly together. Well, if in the same hand, rebuild into a jack is marvelous. At the same time, trashing estates with jack isn't so terribly hot for rebuild as normally it is.
On the other hand, I don't really have a very good feel as to how to play Rebuild, and I have quite a bad understanding of how to play against it.