[Kevin Sevcik]

I think it should probably be noted that declarations about how rare mecanums were on Einstein don't really mean much till after 2007. At least.

2007 was the first year andymark offered mecanum wheels. So pre-2007, the only teams attempting this would be teams with the time and patience to make their own wheels and try them out.

Even then, I think it's a little arguable that they've had much of a chance at shining since 2007. Look at the run down:
2007: Debut of AM mecanums, with all the first-run, low volume problems.
2008: Mecanums arguably weren't much of an advantage.
2009: Lunacy, slicks only
2010: Bumps and plywood under the field reduced the effectiveness of mecanums.

So I don't think there have been all that many years where mecanums were both commonly available and obviously useful for that year's game. Now that may be because they just aren't ever going to be useful to the game, but I'd want a few more games to actually make that call.