I just purchased a DCX3200M and I have never seen a worse response time for user input from any device I own!
Some of my experiences are as follows:
1. Whenever the menu button is pressed on the remote to pull up the guide it takes 5 seconds to show up. It takes so long my wife or I have presses it several times because we think the remote is not working. Then after 5 seconds the menu shows up... what we hadn't realized was that the box had received all of the key-presses and buffered them all up from the remote and the box now proceeds to respond to each and every press made previously because a lack of response from the box... of course delaying 4-5 seconds between each and every cued button press that was made and pull up another guide menu page.
2. Whenever you scroll to the bottom of the guide list when the guide finally decides to come up it takes another 5 seconds to flip to the next page in the guide.
3. The Guide doesn't seem to be cached on the Set Top Box because it takes so long to call up the same menu guide information even though it was just displayed moments earlier.
I really don't know where the bottlenecks are in the architecture to improve the responsiveness of the user interface however for constructive criticism purposes the general suggestions for good set top box user interface design are:
1. Respond or acknowledge any remote key-press as quickly as possible (300ms or less). If you don't do this the user experience becomes significantly diminished and the user interface will seem unresponsive to the user.
2. Try to respond to any data page display result action in less than 1 second.. If you can't respond with data results this quickly then try to show some activity progress indication.... like an hourglass or progress bar.
3. If you can cache data to improve response time then do it!
of the devices.