I'm using a Ford 917 on a 1210, which is really way way way too small to have any business pulling a 6' flail around, but it does it.
Attached FileGreat cut, and faster than the mid-mount deck, which I only leave on for ballast.
You can sort of abuse them as a forestry mulcher, but flails can start getting expensive, fast.
Once I get this thing behind a 50hp+ tractor I'll be in business.
Big advantage vs. a mowing deck or a rotary cutter is that you have very little chance of slinging debris.
ETA: To answer the OP more directly, I've cut my front/back yard with it, but normally only mow the fields as the house yard has some tight spots that you're not gonna get with a 3-point, so I normally cut those with the lawn tractor.
The roller on the flail prevents much of the scalping action you'd see with other types of mowers (though I haven't tried out a finish cut mower.)