My windows laptop is on it's last legs. I need a machine for development and I loved the MacBook Pro I chose for development at Jackpot Rewards. The only problem I have with the Pro is it's price - it is a premium-priced product.
I have a great 24" monitor on my desk at home and plenty of keyboards and mice. Having a very portable machine is not very important right now. These factors led me to the Mac mini. My current work from home is using Ruby on Rails and my development environment is centered on TextMate so my performance requirements are quite low.
Sure, I would have loved to buy a Mac Pro but the price difference is huge for the extra capabilities. If we get to the point of running an office with a few people I will definitely consider it.
I will write again when i have spent more time using it as a personal system and a development system.