Until now we see no problems with the Mac version 
- a pre-order is required for the ALPHA and BETA access. Everybody who pre-orders get a nice special in addition regarding the release of World Creator 2 - something fancy that shows that you participated in the ALPHA and BETA versions of World Creator 2.
However, if you pre-order you get World Creator 1 for free - it might look a bit oldschool and generation time takes a few seconds but it is known to be extremely powerful in creating realistic terrains
Hope that helps