I've been testing WL7 over here for a week. So far so good.
I doubt your prefs files will transfer properly, even on PC. 7 appears to be a total overhaul of the app. The downside is that PC users face a similar learning curve to mac newbies. The upside is both groups will have a very customizable, flexible and powerful app that does things the old ones didn't...
...like DDPs, as a stock feature in the Pro version, and the wonderful Sonnox n/r suite. I've tested the DDP feature in both directions (opening/cutting from existing ddps made in other apps, loading back CD masters as DDPs, and opening/cutting from WL7 DDPs in other apps). Works great with a minor caveat: loadbacks don't recapture all subcodes, due to issues with modern DVD-capable drives (they rely on data services, and don't read subcode). Philippe, the author, is looking into fixing this.
The mac port is pretty good and stable already, but there are predictable issues with plugs. PSP's newest plugs work great, the Master series, not so hot - it's workable, but barely. YMMV depending on plugs you use.
OTOH the mac version doesn't always follow mac conventions, and it's often hard to find things. In some respect it's like DP, with many key features hidden in little mini-menus and gadgets that are only visible in certain windows and conditions. Fortunately, it's not terribly hard to customize the workspace. If you put in a saturday or late night you could probably make WL look/feel like whichever DAW you normally use, at least functionally.
Frankly I'm pleased and amazed that it works as well as it does, since it's essentially version 1.0 on the mac. If first release of major upgrades to Logic and WBP (or OSX for that matter) were as solid, no one would hesitate to rev-up and these forums would lose half their traffic!

-d-