Do you reckon that most Mac mini's come with DDR400 memory? I know that there is some discrepancy between hard drives, with the 1.25 shipping with a 5400rpm drive against the 1.42's 4200rpm drive.
I'm still tinkering with mine at the moment, tried out FC4T3 which seems to work flawlessly, although I've now switched to a dual boot of Ubuntu and Mac OS X.
For those of you who are considering purchasing a Mac mini then go for it. It's almost un-nerving how quiet it is - I'm glad it has the solitary white LED on the front to reassure me that it is actually on and working!