When I was contacted by Dish (they called me) I explained that I had a 722 and an EHD and was leery about switching to the Hopper because of losing my stored material. I was assured that the Hopper would have no problem connecting with my EHD and she would make sure the installer was a level 2 or 3 tech. A very nice young man showed up and had no clue what a EHD was. He informed me that he was new with the company (2 months) and was indeed a level 1 tech. Between the two of us we managed to get everything hooked up and the Hopper had no problems connecting and working with my EHD. Several other problems have reared their ugly heads in the first two weeks, like losing stations from me Custom Guides but all in all I'm quite satisfied.
Some of our CSRs will make up ridiculous crap. CSRs at the call centers have absolutely zero ability to dictate what "level" tech will go to the job. They set up the work order, and DNS then takes it from there and applies the work order to a tech.
Since an EHD is not a Dish-branded device, Dish is limited in being able to help with it, and no...nobody can guarantee something will work (or not work). We can say it generally will work, as the EHDs generally do, but there's too much variability to say an absolute yes or absolute no. For instance, CSRs are supposed to say (if they look and find this info on our intranet) that the EHD should be between 50GB and 2TB, should have an external power source, and be connected to the receiver using USB. I've seen people on this board be able to get things outside of those "requirements" to work, but it really is a crap shoot if they will.