I found this article today and it raises a few good points. If you are in the market for a new website or you are a web consultant, you should read this and understand why prebuilt themes can be problematic. Usually things with a million bells and whistles are weighted down with so many things you will never use, it actually hurts rather than helps you. It can lead to a slow site as well as creating more work for your web developer trying to populate content and customize the theme.
So what is the solution? That's an easy one. Have a custom site built from scratch. I realize that is not in the budget all of the time and I even integrate prebuilt themes for clients (I spend more time stripping them down than customizing them though). Ask yourself, do you really need a Wordpress based site? What can you not do with a static HTML/CSS site that can be done in Wordpress? Weigh the options, speak to someone that really knows Wordpress and determine what you can invest on your website and calculate the possible ROI.
To me the most important thing is site longevity and its ROI. If it doesn't covert, its crap. Think about it. Why try and shove your company into something that is canned? Yes it can be done and I do it all of the time, but is it the best route? To only save $1500 and have to come back in 12 months to redo it or spend a ton of money in SEO? My custom sites convert better than prebuilt themes. Hands down. I even think that Google ranks you better but I do not have data to prove it.
A uniquely designed site, custom crafted with love and tailored to the individual client is always a winner. Now if we can just bring that to the masses...
Here is that article, enjoy.