There are 4 types of DISH Network retailers...
#1 Going through DISH Directly
#2 Going through a CE Store like Rat Shack, Costo or Sears
#3 Going through a National Sales Partner
#4 Going through a Local Retailer
First of all hands down the Local retailers are going to give you the best customer service, and are going to a better installation.
Second of all the national sales partners, are also good to go through. They will usually do a superior job selling the product, but their installation is dependant on DISH Network since all installs are referred through them. There are some good deals through certain sales partners, and if you do your homework you should be able to get a gift card with purchase. SOME SALES PARTNERS WILL TRY TO COLLECT A PROCESSING FEE ANYWHERE FROM $19.99 UP TO $49.99. DO NOT PAY THIS, AS YOU ARE BEING RIPPED OFF
3rd, going through a CE store like Costco, Sears or Radio Shack will probably make for the worst experence in terms of sales, as the sales people at these places don't know anything. They do run gift card promotions, but be sure what you are signing up for if you take them up on these offers.
Finally, do not do business with DISH Network directly. They will not give you any special offers, like you will find with a local retailer, sales partner, or natonal CE Store.
In terms of customer service, if your going through a CE Store or a sales partner your dealing with DISH Network for the service after the sale anyways.