Great introduction to Mac OS / Home Theater PC

I recently upgrade from a 1.5Ghz G4 stealth upgrade Mac Mini to the Core 2 Duo 1.83 Ghz mini and I am very impressed with the performance improvements. With Xbench the Core 2 Duo was approximately twice as fast as the G4 on many tests.
The Mac Mini has a very small form factor 6.5"x6.5"x2" which makes it well suited as a Home Theater PC (HTPC) or for desktop use where space is at a premium. I primarily use the mini as an everyday computer with some HTPC use. The computer looks at home both on the desk and under a TV.
The Mac Mini is an excellent entry level computer or an introduction to Macs. This is not to say the computer is limited in capabilities. The only real limitation over the mini's bigger brothers, the iMac and Mac Pro is the fact that it's expandability is more restricted. The stock laptop hard drive is slower than desktop sized hard drives, and the graphics card is integrated meaning gaming performance suffers. Realizing these limitations, the mini is a great deal.
For those that already own a G4 mini or even a non Core 2 Duo model, the software alone can be worth upgrading for. OSX 10.5 and iLife 08 are included free and are both significant upgrades to the MAC software base. Together they cost £140 / $208. The resale value on old minis are very high, so it is actually cheaper to sell your old mini and get the latest hardware than to buy the software upgrade. The performance boost will also be very noticeable.
OSX 10.5 now supports Linux apps natively and has bootcamp which allows the user to install a copy of Windows XP or Vista onto the mini and run it natively as fast as an equivalent speced PC. This means the Mini or any Intel Mac with OSX 10.5 can be used to run applications on all 3 major platforms making Macintosh's a very good value. There is no longer any need to own a Windows machine to run programs that are only supported on Windows.
If you are after a small computer, a HTPC, a reasonably priced computer, or a way to run MAC linux and Windows software all from the same computer, the mini is a great choice.