I think there are at least a couple of quite defensible opinions about what makes the A class so great (apart from being a really fun boat to sail - of course, no disputing that): (i) the fact that it provides very close and competitive racing - your point I think Mary, and (ii) the fact that its very nature as a very loosely restricted development class has enabled it to evolve the great designs we see today.

I'm sure there is no single right answer to which of these is more correct. It is interesting though that debate about the right balance between tightly and loosely controlled classes has been around a long time. I always enjoy reading the 1951 exchange of correspondence in the NZ sailing magazine Sea Spray about the R class development skiff - the 2nd and last 4 links here:

http://www.rclass.org/1950/