Now that the steroid era has passed I think power is most definitely more valuable than speed. The Reds led the NL in offense last year pretty much without a major speed guy in their lineup. Speed is great to have at the top of the order, but I think most any team would take a power guy in the middle of the lineup over a speed guy, provided they're roughly equal in their power/speed skills.
As for rushing players, I'm with you. I generally don't like it, and would always prefer to hold a guy down too long than rush him up too fast.