Over the last 20 years I've ended up replacing all the toilets in several houses - just don't ask.
Recently swapped out a couple old 5 gallon Mansfields that didn't work very well for new Kohlers (189 from Lowes) and
1) they do a great job - a successful flush every time; and
2) install has really gotten much easier. Everything comes in the box, all the insides are assembled, assuming you can drop the base on the flange the rest is nothing. No fussing to make sure the tank bolts seal, or to make sure the base of the filler valve seals. And the filler hoses all have hand tighten (rather than wrench) fittings.
Recently swapped out a couple old 5 gallon Mansfields that didn't work very well for new Kohlers (189 from Lowes) and
1) they do a great job - a successful flush every time; and
2) install has really gotten much easier. Everything comes in the box, all the insides are assembled, assuming you can drop the base on the flange the rest is nothing. No fussing to make sure the tank bolts seal, or to make sure the base of the filler valve seals. And the filler hoses all have hand tighten (rather than wrench) fittings.