I wouldn't be so quick to dismiss mecanums, but there are better ways to achieve maneuverability - of course, that's another discussion itself.
We used 6" mecanums in 2011 with great success; we had absolutely no problem whatsoever with wheel damage. We did come away from that season with two particularly important lessons, though:
1 - make sure your wheels are always in contact with the ground. Although it seems obvious as the kinematics of mecanum drive rely on all 4 wheels, it's not obvious when your chassis is warped. Following unaccountably erratic driving control halfway through qualifications at CMP last year, we discovered slight chassis warp, on the order of 1/8" to 3/8". It ended up with two mentors jumping up and down on our chassis to fix the warp (we students weren't heavy enough
). After that, driving control was much more precise.
2 - precise speed control is a must. Because the nature of mecanum requires that each wheel be individually controlled to a relatively high level of precision to enable accurate driving, it's imperative that the software is capable of precisely controlling wheel speeds relative to one another. Unfortunately, it wasn't as easy as tossing CIMs into Nanos and bolting them to our chassis. Developing effective speed control took our software engineering team a good amount of time, and it was only thanks to that that we were able to achieve the level of driver control that we did.