I have an ASP 61 two stroke on my plane, brought it second hand with the plane. While it looks to have had a lot of use and at least one crash (busted fin on top of the head), yet runs strong with now issues - though it did take an expert hand to get the mixture right (not my own hand I might add).
From my limited experience with them, if an old used one runs that well, I'd get another one (they are getting more popular down here as well)