If you intend to cut new nuts from blanks and/or intend to do a lot of adjustments then a top quality, pro set of files is a good investment.

I bought a set of "Noman" files on ebay.

http://cgi.ebay.com/Norman-Guitar-Nu...d=p3286.c0.m14

These are not the right tool if you intend to do a lot of nut work. It seems the steel tends to dull a bit to quickly. However, for the occcasional adjustment they work great. I've also heard good things about the feeler gauge, welding tip cleaner strategy. For the occasional adjustment, I'm sure they will work fine.