Only two places to rent from. http://www.lakepowell.com/houseboats.php http://www.azmarinas.com/AntelopePoint/
We have rented numerous times from the first link and are always happy. The second link is new and have nice boats and nominally better pricing.
There really is no "best place to ski." The further you get away, the more likely you will be away from people. Even close, early morning and evening are GREAT. We usually stay close enough to drive the tow boats to a marina to gas up. Lake Powell is more the experience for us, not just 24 hour a day riding.
There have been some good threads on this forum related to costs, breakdowns ect.