If you're going to run a servo-saver (or the car has one built in), then the 1251MG is a good buy. However, if you're not running a saver, I'd look at Futaba BLS551 ($$) or S9551 ($). The 1251MG has all-metal gears that are pretty brittle, so you go from fine to DNF with a stripped servo with very little notice. And it can blow out on a seemingly innocent little tap.
The Futabas, on the other hand, have one plastic gear in them, which seems to give them a little more resilience. I've stripped a 1251MG twice. With similar levels of punishment, I've never stripped my BLS551. But I run servo savers all the time now, because I don't like DNFs.
That being said, the gear sets for the 1251MG are quite cheap, so if you don't mind a DNF a couple times a season, then keep an extra gear set on hand and go for it.
-Mike