there's a sure way to know which is what i've done to prove it's not the remote. use the buttons on the box to perform some commands. i experienced the same lag using the buttons on the DVR. seems like a lack of processing power. needs more juice
I would have to say they either skimped on the ram in the boxes or they just plain need to optimize the software..
The box is the only Complaint about D*, the non DVR's respond better which leads me to my privious statment.
It almost acts like in the windows world when you have a non optimized runaway app that is using to much swap space due to not enough ram.
I notice it the most when recording shows in the backgound