Interesting article about some research done around the impact of graphic design and marketing text on two university websites.
Omniture looked at the universities' request for information pages, changing various elements in the design and copy to see what, if anything, affected enquiry rates.
The upshot is, it depends. Depressingly vague, but nevertheless highlighting the limitations of marketing guidelines - there is no magic formula. You need to engage with your own users to find out what will work for you.
In this study, it appeared that the more sophisticated design - "hero shots", marketing copy etc - had a positive effect on visitors arriving on the page from search engines, and a negative effect those navigating to the page. Those navigating preferred the simple, functional approach.
The question is, I suppose, who would you prefer to receive enquiries from?
Context matters - article by Omniture Industry Insights