I have a 2006 Mini which has been upgraded with an SSD, a 2.33 gHz C2D chip, and firmware 2,1, so that it now acts like a 2007 Mini. It originally had a 2GB RAM limit, but with the upgraded firmware it actually has 4 GB RAM, and can "see" 3 GB.
It's been running 10.7 Lion for two years like a...