If I'm already sleeping when he comes to bed, it's usually not a problem, but I'm such a light sleeper that if he were to fall asleep before me, just his breathing wakes me up or keeps me up. He doesn't snore loud, just a little, but it does wake me... especially now that I'm having to get up to pee several times a night, I go back to bed and can't sleep :)
He doesn't grind his teeth, but he does click them, and it drives me crazy!
When he starts to snore a little, he's usually on his stomach or on his back and has his head craned all the way back. I try kicking and poking, and if that doesn't work I wake him up and tell him to turn over. Luckily, he's not grouchy about it, I think he feels bad about keeping me up... it's not like he remembers me waking him up to tell him to turn over anyway. Most of the time he'll just argue that he wasn't snoring, he wasn't even sleeping (yeah, right!) but he still turns over to his side.