Like with kids it's definitely one step forward, two back. It sounds like you're on the right road though.
With Eric, after owning him for one week, my hands and wrists were covered with little scabs from bitey thing - and when he nibbled a half healed sore from a few days before it positively hurt. Trouble is those puppy teeth are like little hypodermics aren't they?
I'd go to play with him with a toy, and he'd try to bite my hands. I'd go to stroke him, and he;d try to chew. Try to stop him biting with a big loud ouch and he'd just look, or try biting something else (like my wrist, other hand or shirt sleeve, or trouser leg). For a while if he was awake he was trying to nibble a live human. :)
http://www.jersey.net/~mountaindog/berner1/bitestop.htm Gives some good advice, but we found it a little challenging to implement sometimes - When we tried the walk out the room response it was pretty hard, as he usually attached to an ankle. :rolleyes: Shout ouch (in lots of tones to find one that got a let go reaction - result none of em) often just got a look from him, rather than release. We eventually figured if he simply looked at us, and paused, our point had registered. We still had to remove the jaws manually. :)
Now at 5 1/2 he still mouths, but has good bite control, and it only really happens when he's overexcited - nibbling hands (gently) or shirt sleeve - but he's got adult teeth so it doesn't hurt the same - and will stop.
Now I've had several dogs before, and a friend who bred Bernese Mountain Dogs (so lots of time with swarm of pups) and had never met one who was quite so focussed on mouthing, or who you could feel varying his bite while watching your reaction.
Sounds very familiar, and we spent ages wondering if the concept was getting through to him as there was no apparent progress. Thing is looking back, prompted by your post, it's pretty well fixed, but it was fairly slow progress.
He has lots of marrow bones of varying ages to choose from and now will 99% of the time just gnaw on one of those.
Take plenty of time socialising him - we took little un pretty much everywhere with us - town centre, on the trams and busses, to the vets just to say hello, outside the local school, and he was pretty unphased by any of it. When he sits he's probably not sure, so just give him a little time to watch and learn.
Good luck, and make the most of it - the sweet puppy stage passes oh so quickly!
Matt