I don't know anything about how good an investment it would be. Are they going to stop making them anytime soon? I haven't seen prices go up very much for them.
I have two friends who went on a trip to Alaska. One bought the Marlin 450, and the other bought a lever gun in .45-70. The .45-70 was much easier to shoot, recoil very managible, accurate. The Marlin 450 was not as accurate and the recoil was stout, to say the least.