Wayne, this would be an honest review, so bear with me. (I have experience in PPC biz).
Wayne, well, think about it. Every PPC engine that has ever become popular is because they have something unique about it - presense. Right now I see a template-job, which should not be IT.
It also looks a bit like a domain name templates that make money of clicks generating from their ad-codes.
Basically, there are thousands of other engines that look just like this. Be the one. Stand out!
So, here is what I would do about your search engine to make it look absolutely lovely and appealing.
1. Change the template - make it a unique one. Simplicity here is everything. Look at BrainFox.com or LookSmart.com
2. Don't use tropical colors. They make it unserious.
3. Try to make less of most popular "pre-searched terms" on your home page - they just make you lose concentration of what you really wanted to search for.
Remember of the strategy - if people wouldn't recognize a PPC search engine from its look - they will more likely to search it. If they just feel you'll make money off their search - big chances are - they'll go away.
If I think of something else, I will certainly add here.
Good luck with the project, Wayne!