I recorded an HD video program (Trading Places) and an HBO HD movie last night and the PVR worked great. I can't tell the difference between live and PVR.
I don't know enough about the OS since this is my first PVR, but the guide looks EXACTLY like the Time Warner program guide except you have an option to record a program in addition to tuning the channel in immediately or setting a timer. The guide only goes one week ahead. When you select record, you get a screen that allows you to fine tune the time, specify whether or not you want to record once or regularly, and how long you want to keep the recording for. When you invoke the "List" you get a list of recorded programs that you can play, rewind, block, etc. and when you play, there are three levels of fast-forward and fast-reverse.
Just a note - on live viewing, I am getting an HDCP error message (on various channels) that blanks out the picture and instructs me to hook up my display via component because my display doesn't support HDCP. This stays on for 30 seconds or so and then the picture comes back. Not sure where the problem is since my display is HDCP compliant.