Hey Tony, I use a 24" Imac with 4 gig of ram. As far as video editing I love it. It will get it done cleaner than a pc, but I still have to run one or two pc programs on my Mac. There are certain things like my html editor that is just better on a pc. The best free program for editing video on a Mac is Imovie 6. (not the new one, it sucks)
http://www.apple.com/support/downloads/imovieHD6.html
Here is a trailer to a movie that I edited on imovie 6.
Thrust Trailer
As far as converting to different formats (DV,FLV,WIN,AVI) it is best to use a program called Visual Hub.