Wordpress as a way of building data driven websites for small to medium businesses has really come into its own over the last 2 years. We find ourselves building more and more websites using WordPress as it gives the advantage of a quick take up with a plethora of themes and plugins ready to go.
Of course you still need to know a bit more above and beyond WordPress to have a succesful website but wordpress, in the right hands, is a great place to start.
SEO is possible in Wordpress but usually only when you have the right plugins and the knowledge to drive them. No plugin will do the research to tell you what keyowrds are right for each website or the best way to use them in general content, but with the right plugins an experienced SEO person can get the most out of WordPress.