CSS frameworks

For the last year I’ve been using a set of bare CSS templates I’d built as the basis of the websites I design. I’m thinking of updating them so I need to revisit the following:

Font sizing

Currently I’m using pixels with a conditional stylesheet for IE that contains font sizes set in the equivalent percentages. The theory was I set up the IE sizes last when the site is basically finished, all I had to do is run through the main CSS and match any pixel sizes to percentages. The main problem I had with this was the addition of elements in the site after I had designed the pages led to the IE sizes not always being set, a problem with project management really and there being too much interpretation of the spec.

Image replacement

Should I be replacing say an H1 tag in the header with a logo image? This would make setting up PDA versions of sites easier but what are the implications of this? What about those people who have images switched off but CSS switched on?