AFter hearing all of the good stuff about Mac, I really want to upgrade. However I have thousands invested in my pc. Do I have to repurchase everything from adobe (cs5, Lightroom 4) over again at full price? Thanks for the info.
For CS5 you should be able get a cross-platform upgrade to CS6 for regular upgrade price. Since Lightroom 4 is current version, you can get a platform swap for a minimal processing fee. Both instances you need to contact customer support.
Another option is to join the Creative Cloud for US$49.99/month.
One benefit for owners of both Mac and Windows is that the Cloud allows you to activate the software on both Mac and PC (max 2 activations in total).
(a discounted rate is available for the first 12 months since you already own CS5)