I don't think it just takes title and meta tag - it should be using an excerpt. At least my copy of nutch does that. So if that's all you're getting, I think something wrong on your end.
In terms of improving the quality of the search results, there are weightings you can change that will affect the rankings. I've forgotten where, somewhere at the config level. It'd take a programmer to change them I suspect. that being said, I've never had much luck getting 'great' SERPS with nutch - 'good' is about as much as you can expect.