yeah, whatever.
When doing the weighted crunches, I use a decline bench. Grab a 65 (or whatever), cradle it to your chest, and use a 2-1-2 tempo. Go down to parallel to the ground, and come up until the resistance lessens (just before you're perpendicular to the ground). 2-3 sets of 8 should be plenty.
Mjollnir, the ab wheel does work the abs quite well, but it also works other muscle groups, which most people already account for in their routines. hanging leg raises (done on a chin-up bar, actually compressing yourself in to a ball, not just using your hip flexors) and weighted crunches are MORE than enough isolation for your abs, considering most people ridiculously overtrain their abdominals anyway.
Just because an exercise is hard to do well does not mean it's superior, by ANY STRETCH of the imagination.