Why do I use a tivo when I already have a HTPC?
Because it's cost effective.
DirecTV charges $5 per additional receiver per month and a single $5/month tivo fee.
My DirecTV Tivos have two built in tuners.
So my two tivos cost me $200 in hardware, and $10 extra per month. Each tivo has Optical audio output and s-video quality.
To get the equivalent in HTPC, I'd have to buy 4 capture cards at $100+ each, 4 Tuners (I could get em free at sign up) and pay $15/month extra for the tuners.

So my monthy costs are actually LESS, my video quality is better(no redigitizing), and my wife and I both have our own tivo's to set up season passes on.
We have had NO arguments about who gets to record what, and I like it that way.:)

With some effort, you can get the tivos to talk to each other. I can watch a recording either upstairs or downstairs. Nice, eh?

The downside is that I can't playback my own video files. Otherwise I'm happy with the tivos.

My 6.2 howto

Mostly written for my reference, since I touch my tivos about once a year.
Maybe others will find it useful.

restore stock 6.2 image to drive.
killinithd a 3.1.5 kernel
install 3.1.5 on active kernel partiton. (For mine it was 3)
dd the active root off the restored 6.2
disable iptables
add ethernet drivers
add shell utils
add vim
add wget
enable telnet
enable serial console

After boot, run superpatch.

Useful reading for switching to 6.2

6.2 collected info

Superpatch 67all(hmo-mrv)

Walkthrough for upgrading to 6.2 on already hacked unit

Series 2 U5/Monte hacks