i wouldnt say brilliant. very good yes......not brilliant.
i only know what i do, cos my ex had 4.....and i was stuck with them, when she ran off with my mate (who we had put up for 4 days as he wife ran off with someone else...........)
bite wise, i have had worse bites, stings etc. from snakes and insects and arachnids. they can give a nip, but its more of the human reaction to pull away. just have a little confidence and let them get to know your smell
they are pretty smart, so need to be stimulated...they care very very good and cold temps, but i belive warm//hot temps are bad. (i mean before you would expect to be bad)
i dont like ferrets as such, but i can think of many worse pets.