Our boy is nearly 5mths old, and is incredibly gentle with us, no more play nipping etc He is however incredibly rough and vocal (play growling) when playing with other dogs. Some dogs, like other Jacks and larger dogs are fine with him as they tend to play very similarly. It's the little white fluffy breeds that just want nothing to do with his rough housing, he will get growled and snapped at pretty quickly, but he pays no attention and continues to pounce and try to play, I quickly pick him up or put his leash on and move him away when this happens, but he just does not register that some dogs just want nothing to do with him. It also doesn't help that our cat plays just as rough as him lol
I'm worried that one day he'll do this to large powerful breed and he'll cop more than a growl and an air snap..

Some people say "oh he's a typical Jack Russell", others say "That boy needs training/obedience". Is he being a normal puppy? Should obedience classes start asap? I have always had laid back placid breeds in the past, this is my first foray into Terriorhood, and i am constantly second guessing myself.

Other than this, he is travelling along perfectly. He truly is a great dog!

Little white fluffy breeds aren't suitable play partners for many terriers, too much temptation to pick it up shake it and treat it like a toy

You may be right monkeyj. I think Nugget needs to stick with more compatible playing partners.

All dogs need to be trained and have obedience to their owner. You should be more interesting than other dogs and if you aren't there lays a problem.
I do not like rough play between dogs it can quickly turn into something much more and the more they practice a behaviour the harder it is to stop it.
Nothing wrong with running around with other dogs but shoulder barging, running into other dogs is actually very anti social. Dog parks are also the worst place I see this happen and owners stand around and allow it.

Fact is dogs don't necessarily NEED to be playing with other dogs, especially strange dogs.  It's all too easy for such playing to turn into a fight, although maybe if he picks on the 'wrong dog' dog and within reason, gets bashed up, that may stop him from doing what he's doing at the moment.   I don't like other dogs running up to my two (especially if mine are on their leads) unless I know the dogs, and owners who allow this are being unwise, if not inconsiderate.   I had a neighbour who thought her two should do this when I was out with my multiple numbers, when we had bigger numbers, and it made keeping mine under control VERY difficult.   To the point that if I saw her approaching with her's, I'd take avoiding action!  As said, your dog should be focusing on you.

Classes might be a good idea, especially if he isn't listening to you.