First off... I think the feed rate overide only affects the FEED rate not the rapid in the later versions of mach.
second, rounding is present in all machines, as Art stated, fanuc, mach and other machines capable of constant velocity. the thing is, most machines that do not have this problem use big enough servos to handle scary accelerations which make rounding a lot less. If you do not use constant velocity you SHOULD NOT see rounding.but maybe your machine is too flimsy that when it stops it wiggles a bit and and bad cuts are seen. if you set your acceleration way down, I mean WAY down, and use exact stop, im sure you wont see this, but then again, cutting times will go way up. so it is basically a trade off situation if your machine cant handle this shaking.
As for light at the end of the tunnel, well there´s QUANTUM, which is a whole new approach to things, which in my opinion is the way of the future, and I am sure there are not many controllers taking that approach.
Regards
Fernando