I've had my HTL-HD for about a month now, and thought about giving feedback myself, but dgordo covered it: great unit, love it, slow menu and that's my only complaint. However, I noticed that this is your first Tivo; mine is also my first, and is in fact my first PVR, so let me expound on that.
First of all, believe the hype-- Tivo WILL change the way you watch TV, and if you watch a good deal of TV as I do, it can change your lifestyle. I never watch anything live anymore because when I watch it delayed I can skip commercials. And besides the basic pleasure of avoiding commercials, you might be amazed, as I was, at how quickly you can watch a show with the breaks cut out. I mean, logically I knew that a prime time hour long show clocked in at 42 minutes when the commercials were removed, but actually sitting down to watch an evening's shows and getting those 18 minutes back, well, it's an experience.
I'm also enjoying the ability to watch shows that I otherwise wouldn't have given a chance because they were scheduled against some other show that I already watched regularly. And when digital recordings are so easy to schedule, watch, and delete, without eating up video tapes or some other limited-lifespan medium, you will find yourself recording a lot more stuff and giving more shows a chance. In case this post makes me sound like a mass-media pop culture addicted couch potato, you might be interested to know that the primary expansion in my viewing is for educational programming on PBS, Discovery, et al. Before the Tivo and its two tuners, I would have missed these one-time event programs, like the recent Nova Mars rovers special, because I had something else to watch.
So yeah, PVR in general is great, Tivo is pretty awesome, and HD Tivo is just fantastic. I still, after a month, marvel at the ability to record shows, especially HD shows, in PERFECT digital copies, even recording two at a time while watching a third show I recorded earlier.
The HD Tivo gets high marks from me; now I just have to hope that, if I am forced to move to a different PVR brand when MPEG4 becomes the standard, the replacement has the same quality that Tivo brings to digital recording (yes, as I said, I haven't tried other brands, but the critical feedback, both professional and amateur, always gives Tivo better marks than other PVRs).