I'm got a Brother my mom gave me when I went off to college in '92. It's served me well. When I finally brought it in to repair the tenstion that was WAY off, the repairman told me that he doesn't like the Brother models, b/c the casing is hard to get into - apparently, you have to unscrew a bunch of stuff to get to the parts.
BUT it's been great since the tension was adjusted. Personally, I leave adjusting the tension to the pro's - I'd rather pay a lil' $$ than break my workhorse.
Mine's a Brother XR-31 I don't think they make 'em anymore.