I agree with CPanel & Fantastico being included is very important. I have a large update I am working on to provide a variety of information to webmasters and resellers. It is time-consuming, but, that hard work will show and please your clients for the long run. While maintaining your current reputation that you gained by providing quality services, you can also increase the length you will go to please a client. Although, common sense is required at all times, don't go too far it can hurt if you do.

I Agree with Caronet-Hesham. These are the major characteristics of a good hosting. As to the Panel - DA it is pleasant to me. And unique templates - are good too

And having backup as often as possible.