This is, hands down, one of the best allies in the game; the best? It's certainly a contender. 2 resources for 2 of any one ability is really nice, but 2 for 2 is especially nice for .
Add on top of this the fact that you get a conditional +2, it starts to look more attractive. The response ability really pushes this card over the top though, giving you the ability to reliably quest with Pippin every round and only wait for his conditional attack bonus when you can be sure it'll trigger.
So really, it's 2 resources for 2 every turn, and an additional 2 on some turns, which is incredible value.