I made the move to WordPress 1.5.1.3 today. It seems to be a little nicer in the administration area and some important security holes were fixed. Probably the biggest change is the move to themes. I'll spend the next week or so creating my own theme to match my main site. Until then, enjoy the captcha-free commenting...
I like the new WordPress, I’ve been meaning to update omsu for a while now. To kick off your theming, why not have a look at some of the theme galleries for a starting point?
Patricia Muller did the popular Connections theme, and now she’s doing some stuff on WP Themes.info.
WordPress has a list of lots of themes in their codex.
The Kubrick theme (the basis for the WP1.5 default theme) is a fine starting point, but it’s all over the place.