Over the past couple of years I've played around with premium Wordpress themes with varying degrees of success. The businessman pragmatist in me likes them but the developer doesn't. I've noticed a lot of improvement recently and some of them represent pretty good value for money. In fact the actual cost of them is fairly negligible in the grand scheme of things. The cost lies in the clean up and customisation. Here's my article about what to look out for when picking a theme.