I don't think weight is important. We have this discussion all the time in the road cycling forum.

Like mentioned above, it's all about power per weight ratio. If you and your bike weigh a lot, but you can sustain a high ratio, then that's good. You could always get faster by training for more power, or even easier, losing weight (unless you're a twig).

Body weight makes up a large amount of the total weight of a rider + bike. It's usually easier and cheaper to lose weight off yourself... or even your tools you carry.

When you look at it, it comes down to 180 pounds going up a hill (150lb rider, 30lb bike). You can change some figures around, but the weight will be the same. In my opinion rotational weight does help, but not as much as I think most people believe.