Atlanticfire, I have an 1894 Cowboy Limited in .45 Colt, and $625 is a pretty decent price for a new one. I like it quite a lot, it's quite the death ray with +P loads. I bought it over the .44 magnum because of its better rate of twist so I can shoot heavier weight bullets (not that the 44 can't, but they won't be very stable). The so-called "deep cut rifling" as far as I can tell is just plain old regular rifling. I'm told Marlin used to use microgroove rifling, but that isn't as optimal for lead which is what most people want to shoot out of their lever actions, so they switched to "old-school" rifling. Don't worry though, it will still work just fine with jacketed bullets. My only word of warning is that it can be costly to shoot if you don't reload.
EDIT: Looks like ArmedBear beat me to it