There seem to be almost as many comment presentation styles as there are blog templates.
If you want to see how some of the more attractive implementations look drop by Smiley Cat who has posted a collection of them
They’ve also got some nice tips on how to layout your comments:
10 Tips to Improve the Comment Section of Your Blog
Blog Comments Style
Good links, especially the tips. I’ve been meaning to do a design overhaul on my site. I’m no good at CSS though.