Rats make very good pets. Unlike many other small animals who just live and tolerate handling, rats can become very affectionate like dogs.
Pet rats are not riddled with disease like some of their unfortunate cousins, they are just as clean as other small pets - more so than guinea-pigs and rabbits I'd say (despite loving guinea-pigs too).
Only my most nervous (also the newest and youngest)rat bites, and even then only occasionally when she feels threatened. (As any self-respecting animal does). They are easier to handle (particuarly for children) than smaller (wrigglier) hamsters and mice. But more entertaining than guinea-pigs due to their intelligence and tendancy to build relationships with their owners.
I have a four strong female rat pack, in a cage big enough for six. I've owned both females and males. In general, males are lazier, cuddlier, bigger and more aminiable than the girls. The girls are generally more active, entertaining and rat-centric than the boys. That said, I've got a very cuddly doe. Pick girls or boys and keep a pair (or more) in a large cage with a few toys to keep their minds active.
As for not choosing rats just because their wild cousins are considered pests by some - ridiculous. Mice and rabbits are also considered pests in this country and in other regions of the world I bet gerbils have a similar role, as do dogs, cats and other Britain favourites.
That said, if you do have a wild rat/mouse problem, make sure that your pet (and human) food is stored in airtight containers. I'm sure wild rats would appreciate specially formulated food but you won't. Also make sure that your rats are well secured when you are not supervising them, the last thing you need is a wild rat mating with several of your sweet females... you'd be over run with the offspring! ;)
Spirited