Even though the HDVR3500 is a dual core instead of quad and mine has only 16 GB internal storage instead of 64 GB, I wouldn't want to return it. I really like this receiver a lot, so far.
Navigating through channels is real simple, push OK, up/down, left/right, to whatever channel you want and then hit Ok again, done. Real easy. This is the first receiver I've had that my wife and daughter can use without having to ask me any questions and they're not afraid that they may mess things up by hitting a wrong button.
The Positioner Setting menu is great, with the step move and continuous move options and store position option right below them, I like that a lot. Very good control over sat settings/functions in this receiver. As a receiver, it's the best one I've owned.
As a streaming device though, it pretty much falls flat on it's face there, my Pi2 is way better than the HDVR3500. The XBMC on the HDVR3500 is too crippled and slow to be of any real use to me and IPTV nearly maxes out the cpu on mine at 96% and chokes, neither work very well for me. But...that may change with future firmware updates and as a receiver, it's definitely my favorite of the ones I own.