It's a tool and just like a hammer, a little experience will tell you when to use it and when not too. I personally think using them for forms is a reasonable case if it suits you, I prefer the lighter markup I get with simple divs in forms though. You will find eventually that the rigid structure of tables gets a little annoying.

In the past we've seen huge messes of tables nested upon tables which creates bloated, inflexible HTML. This is usually done by people who would create huge bloated messes of divs anyway. What you should really be focusing on is creating clean, valid markup written with a sense of style and care.

CSS frameworks like Blueprint can make getting started with layout a lot easier for you if don't mind having an argument about the abuse of CSS as well.