I use Soundforge on my Mac under VMfusion4 and its perfect.
So if you already own Soundforge , you can buy VM Fusion for about $40
You can run it in a window so it looks just like a mac program, you can pass data to and from it.
I tried Peak and I unreservedly hated it. (In fact I'm selling my copy in the SOS reader's Adverts)
Audacity is OK too but lacks the bells and whistles.
Hope this helps
I'm doing the same in Parallels and its very quick and stable.
I still can't believe that Sony refuse to go near the Mac, as Peak is awful and alot of Mac users I know come from Sound Forge on the PC and there's nothing the same on the Mac. So a VM maybe your best bet.
I also use Reaper which is very close but not quite there as a direct SF replacement.
Most Reaper users don't now use an editor as it is very flexible but I just got to get used to it i suppose.
If only Cockos would update Reaper to process fx on the timeline, and genuine area selection (which is the top feature request) then it would make a perfect editor for OS X, as well as an excellent DAW.