I have to say I agree with Jimjams (again ) that I found it easier to deal with my kids being bitten, hit then when it was my DS doing the hitting. He went through a stage around 2ish where he would bite VERY occasionally.
On the other hand, all 3 of mine have been bitten, trodden on, pushed, shoved and hit during our years of Toddler Groups/playgroups.
If you have more than one child, it is nigh on impossible to provide 100% attention - it my case I had 3 under 4s and if I had been kept in "isolation" due to DS1s biting, then I would have gone bl*dy insane.
I probably won't be popular for this comment but from my experiences and mothers I knew of, it was the ones who only had the one child who condemned the "biter/hitter" - the others accepted the fact that these things happened.
I can remember myself when I had DD1 - my friend had 2 toddlers who I thought were VERY boisterous, aggressive etc and my little darling was never going to be like that! Obviously my little darling did become a toddler who wouldn't share, pushed kids out of the way etc etc