I've got to be a bit of a contrarian on this point. To date, I've had a chance to grind with darn near every commercially available machine, and although I agree with Ed that some of these spend more money being dressed up and pretty without offering the meat of what makes a grinder worthwhile, I don't think the KMG platform is necessarily a good one, and certainly haven't found evidence of them being built to tight tolerances or precision. Quite the opposite, in fact. I wrestled with getting my own machine right for the better part of 45 days, and it's still only 'good'. The advantage to the platform, and the reason for it's success, is that Rob wisely chose inexpensive cold rolled steel for the bulk of the chassis, which is cheap, tough, and pretty flat. He doesn't, however, necessarily maintain tight tolerances. In his defense, these machines are first and foremost built to be inexpensive. That's important to remember. Having said that, both idler wheels on my stock platen were drilled and tapped crooked, the finish on my tracking wheel was rough, the axle for the pulley kit was bent IN THE MIDDLE, and even a couple of the bolts holding the tool arm parts together were stripped. Since my friend and I started making the direct drive kits available, people have come out of the woodwork to complain about their machines to me.
If I had the money to do it all over again, I'd invest in a Weurtz TW90. Of all the machines I've had a chance to use, this one was head and shoulders smoother than all of them. In fact, there is no close second. Brian Fellhoelter's Ubergrinder would be a good runner-up, as would Drew Riley's new machine, I suspect. I haven't used his yet, but his engineering looks quite sound. I've see Ed mention in the past that he had a bad run-in with Bader, but every experience I've had with them has been stellar, and every machine I've ever used that they made was perfectly consistent. In contrast to this, I don't think I've had a single encounter with Rob Frink where he didn't make me feel like a third-rate citizen, and I've yet to grind on two KMG's that felt the same, or that didn't have issues.
I think that's the most important part of discussions like this - everyone really needs to do their own research, and by all means GET OUT AND GET YOUR HANDS ON THEM. Experience these things for yourself! NO ONE has all the right answers, and everyone has an opinion - form your own!