I have to say I enjoy reading the san-serif fonts better than the serif ones. The serif fonts have a nice classic look to them but I think it terms of reading the san-serif is slightly easier on the eye.
I like arial myslef. But I guess it depends on the design. I'd definitely try to match the header/banner/title styles.
My new WP blog is coming together nicely. http://StephanieCrawford.net
It's been a ton of work, but a great learning experience. I think I've got more text in my titles, descriptions and key words than I do on the screen! Ha!