Well, those are basically the 'standard' classes we've always used. Personally I think that things would be a lot smoother state-to-state if we all went with the AA/A/B/C/D/E/Y classes suggested in the USMTA's proposed rule changes for trials (
http://usmotorcycletrials.com/wp-content/uploads/2006/07/Observed_Trials_Proposed_AMA_Rules_2006.pdf)
The idea being standardization across the country. As is, if you go to another state (or a national) you have to guess what class to ride in. Very confusing. Enduro guys don't have this problem. They know what being a 'B' rider means in an AMA-sanctioned event.
Unfortunately I don't know that the USMTA has made any traction with this in their proposal to the NATC/AMA last year.
So I suppose for this year I'm in favor of 'the usual' classes. But I strongly think we should consider a change for the future. It would be one more thing that would make it easier for riders in other disciplines to transition.
Anyway, that's what I think.
Bent