That is correct. He has been very good at each level, but has hardly made you go "WOW, I can't wait till he gets to the Majors!". He has show pretty good power potential, but not 50+ type power like a Ryan Howard. He has show a good bat, like .280-.300 type, but not above that. He has show some decent strike zone recognition, but nothing to indicate a #3 type hitter in the Majors type.
But he is the unquestioned best position player for the Astros and has been for a couple of years. The problem lies more in how damning that is for the farm system, than his greatness.
I think he will probably be a good .285/35/100 type guy, which isn't shabby. I think Carlos Lee is probably his ceiling if you want to look at a ML equivalent. But I think that is his ceiling, not expectation. Projecting players is sometimes very hard to do, so who knows.