Balliol has now done something hilariously impractical with staircase 22 where they have stuck toilets in all the rooms. It'll probably be fine, and better for conferences, but me and a friend couldn't stop giggling about it when we tried to think out the logistics of having someone back to your room...then getting out the bed...walking one foot...going into your tiny, thin-walled bathroom...and having them hear EVERYTHING. Because you can hear EVERYTHING throughout the staircase - there's this weird piping thing where you sit in the toilet, and hear conversations from someone's room at the other end of the hall and up two floors. Admittedly we were very drunk at the time, but when I sat on the bed, and he went and stood where the toilets will be in his already tiny tiny room, we were literally about a foot and a half apart, and it just seemed really unpleasant and funny all of a sudden.
There are also some real ensuites in Staircase 2, but if ensuites are your thing, Balliol probably isn't for you.