I wouldn't be put off by James Baillie Park because it is ran by Unite - i live there and i've never had a problem, nor have any of my friends. The flats are really nice and very social. With ragard to maintenance - generally things are sorted on the day/day after you hand in the report form thing. Its also in a great location - you can walk to headingley in 10 mins, and to uni in 15mins : its ideal for both study and social things. Town is about 25-30 min walk which is really convenient. Personally i would say it was the best self catered halls...
Some info about the others if you want :
Dev - nice looking, basically same location as James baillie Park, good social things, rooms not as nice as other halls, tends to be inhabited by a lot of stuck up people which i know has affected one of my friends 1st year due to the "posh" environment.
Boddington - long way from uni, some blocks are really dated and not particularly nice, very social, close to sports pitches, you WILL buy a bus pass which sets you back over £150 for the year...
Any others you want some info on?