Here is the problem, in the software development world, your testing would have been called a late alpha or a closed beta test.
You have a vested interest in the product since you sell them. A true beta test is when people outside of the company (actual customers) test the hardware and software. Microsoft wizened up to this process with Windows 7 and held a public beta that lasted over a year for anyone who wanted to participate. As a result Win7 released as a viable product that has seen many different installation posibilities etc. With Vista they did internal testing and a very limited public beta.
Dish could do two things, first to test software/new features, have a way for the consumer to volunteer, and a way for them to revert the receiver to production factory settings. DirectTV offers this on certain receivers by entering a code that one can find by doing a little googleing.
Second program, test new hardware. Dish can come up with criteria to qualify as a hardware tests ( user for at least a year, already has specific receiver, etc.) then have them pay a deposit of $x, like $200 or so, sign the usual paperwork and let them use it as a second reciever in the early stages and then as primary later. when the test is over, they receive the production model for the deposit cost (not a lease.)
This type of testing is much more accurate than having a dealer test the new model.