Coming from a similar situation as yours (roughly 2 acres/p.o.s. craftsman) I just bought a Simplicity Champion a few weeks ago, and I love it.
[URL="http://www.simplicitymfg.com/products/zero-turn-lawn-mowers/champion/"
I've used it 3 times now, the lawn 'n weeds looks great and I've saved 2+ hours each time; also, the suspension on it really is wonderful coming from the solid axle of the lawn tractor.
G'luck on your search.