Ian,
It does not run natively in the Mac OS, you do have to use either Parallels,
Bootcamp or VMWare Fusion.
Currently I use a Bootcamp partition with VMware Fusion, it has proven to
be the most reliable for me. You really need about 60GB partition to make
sure you have enough room, I started with a 35GB, reformated to 45GB
and finally 60GB.
RAM... you need at least 2GB to run any of these comfortable, I am
running a MacBook Pro with 3GB and I have run it on a MacBook with
1.25GB but it can be very slow at startup and some of the running Mac
applications.
Hope this helps.