Here is a comparison I posted on an auction:

Once you've got TiVo, you won't want to watch TV without it!

TiVo has the best user interface ever, MySky etc are poor imitations.

You can fit a huge hard drive!

Allows you to automatically record from any set-top-box (STB), examples include:
Sky satellite
Telstra cable TV
Freeview satellite
Freeview terrestrial

With the addition of a PAL tuner you can record analog VHF/UHF broadcasts.
With a 'dual audio input' modification you can record from two STBs (not simultaneously).

Advantages over the offical NZ TiVoHD
-WAY less software bugs!
-record from STB
-record analog broadcasts
-guide data for 'additional' channels
-much cheaper
-add other cool software or hacks
-customise advanced settings (eg 30 second skip, increase live TV buffer length)
-connect via built-in dialup modem if you don't have broadband.

Just so you can decide; disadvantages compared to TiVoHD:
-standard definition
-record only 1 channel at a time
-computer skills required

Comes with:
-Remote control
-Infrared transmitter 'IR blaster' (for controlling your STB)
-power cord
-HDD _Gb preloaded with TiVo software modified for NZ
*does not include network card*

Extras I can install if you win the auction:
Network card
Nice panel-mount network socket
PAL analog tuner fitted
Dual input modification


Note that since this is a customised device you will need to be a little tech savvy for the odd maintenance or troubleshooting task.
If you are in Christchurch I'm happy to give you a hand with it. Otherwise I can do a fresh software installation, ready for you to plug in and run through the 'guided setup' on your TV.

We have both TiVoHD and a Series 1 TiVo (and a Series 2...)