For non commercial use, I think its hard to beat the value of an MTD/Yard Machine.No its not a toro, tecumseh or honda, but they run well, hold up well, and don't cost near as much.
Take a look at one of their plain old push mowers. Get one with high wheels on the back, and a large engine (5HP or more). The bigger engine will let you mow grass as fast as you want to push the thing in most cases. Its also built more solid and will hold up to occasional abuse, like hitting rocks and stuff on accident much better. We had a 3.5 or 4hp mower once and accidentally hit a hunk of concrete(fell off a truck and landed in our yard) mowing a ditch along the road, it bent the crankshaft. The 6hp MTD we have now has seen much worse and is still running strong.
The high wheeled models push much easier. I really wouldn't get a self propelled. They go one speed, and its a pain the ass. If you want to mow faster you end up pushing the thing any way. In heavy grass, its robbing you of power needed to turn the blade.
They all have briggs and stratton engines. They're simple and reliable. Make sure it has gas and oil, and it will probably run. The most likely thing to wear out will be the deck, and if you clean that out a couple times a year you'll be in good shape on that too.