I have 3 boys, and a baby girl. The circumcision shouldn't bother him at all. Just keep it clean as you would the rest of his body, it will heel up quickly.
Yes they will pee on you every chance they get. However, my little girl peed straight like a boy at first, so maybe it's a baby thing, not a boy thing :)
There boy parts aren't as sensitive as little girls. None of my boys had UTI's or anything, just an occasional diaper rash on their bottoms.
The main difference I've noticed between the boys and my girl is the energy level. The girl is so laid back and content. Doesn't fuss a lot, she's just pleasant. The boys were (and still are) all over the place! They never run out of energy. They tare up everything. They crash their toys together, throw them, take them apart. My girl is only 9mo, so I don't know if she'll be equally as destructive, but going by her current demeanor, I'm guessing not.
Boys can be super sweet too. Every time they go out to play they pick me flowers (their really weeds, but I love it all the same), give me lots of kisses and hugs.
I've been told that boys are a handful when they're small, and are a lot easier when they're older. Girls are wonderful when they're small, but are a mess when they're older. We'll see!