When I play OKW, I always go for a PUMA as soon as possible since it can deal with Infantry and Vehicles quite well in the early/mid game, before one can bring out a real Medium Tank.
So far it was very effective and reliable. I also agree when palying against it, I have the same impression as Barton sometimes in terms of overperfroming for its costs.
I found Smoke grenade pretty handy. It either forces the MG to reposition or you can move on top of the MG and engage it from close range outside its firing arc.