I prefer to make a 2nd style set called "excel", it makes the forums look like an excel document, all images taken away, just text, very corporate looking. Great for browsing at work on a DS3 connection!
My site is dialup friendly, but I am always working on making it better. By utalizing gzip, my index page has 11.2KB of text (down from 64.8KB unziped) and ~20KB in images. However, even then, the site looks great, almost a "broadband" look. Optimizing the site for dialup users really helps on the bandwidth charges as well.