Being from the UK, we're used to high prices and generally being a bit more boxed in so myself and other Brits I know generally feel that life in Japan compares well. The lack of opportunities for work other than English teaching seems to wear people down though.
It's true that apartments are smaller (and draftier) but you can afford, on a teacher's salary, to socialise in izakaya, restaurants and karaoke in a way that's unthinkable in the UK unless you're a top 10 earner. A nice place to live just doesn't seem as important to me any more.
I do think you have to be a pretty negative person if you don't enjoy being here for at least a year or two.
Here is a rather positive Hub on the subject of coming here to teach.