I have never heard anything good about Prime, and Stevens is a little different.
Stevens does not have a lease purchase program. It is a straight lease. They lease you a new truck for 2 years. It isn't cheap, $600. a week plus 3.5 cents a mile maintenance. The benefit is you get a new T2000 with full warranty. If the maintenance is done correctly you should have no major problems leaving you with a nice nest egg in the maintenance account at the end of 2 years.
It may be true that you are buying their equipment for them but you are doing the same thing as a company driver. The average take home should be 20% more when you lease and they help you make that, after all it is their truck.
Stevens seem to be more honest than the companies with a lease purchase deal. Lease purchase deals lead you to believe you will own your truck when you most likely never will.