Since the introduction of the SD70's several years ago, Legacy is DCC compatible. You don't have a million CV's as in a Tsunami decoder, but there is basic DCC functionality to satisfy most DCC operators.
As to MTH's DCC compatibility, we'll know soon, but it is present in any Proto-3 O scale or HO locomotives.
At this point in time, I would suggest going HiRail and use Kadee couplers. Brooks Stover does this to great effect on his BC&G:
I've yet the see anyone complain about the rail height (AM track) or deep flanges in his articles published in Model Railroader or Narrow Gauge and Short Line Gazette.
95% of the time you're going to have to purchase Kadees if you were to go the full scale route anyway. With Hirail, you'll have access to a slightly wider range of locomotives and won't have to cough up the extra dough to convert the wheels (like I did) on the likes of the Lionel SD70's and ES44's.
While traditional S and a fair amount of HiRail stuff will go around a 20" curve, I would suggest 27" radius as a minimum. This is roughly equivalent to 18" radius in HO and will handle most equipment, scale or HiRail.
Rusty
