"Is it guaranteed to have true rendering/display parity with the OS X variant?"
No. Last time I made a hackintosh running Safari on Win and Mac sometimes produced different outcomes in certain scenarios. Things might have changed though.
> I'll put in the time to boot into a Windows partition and double-check IE9, but when it comes to OS X/Safari, I've got little recourse but to crossing my fingers and bank on Safari's Webkit rendering being the same as (or close enough to) Chrome in Windows and Chromium in Linux.
Might want to try the Windows version of Safari then. The JS engines in Chrome and Safari have some quirks between them and can behave differently in some scenarios, mostly things that JSLint would catch though.
I'll put in the time to boot into a Windows partition and double-check IE9, but when it comes to OS X/Safari, I've got little recourse but to crossing my fingers and bank on Safari's Webkit rendering being the same as (or close enough to) Chrome in Windows and Chromium in Linux.
Safari DOES have a Windows version, but I've never seen it enter into the conversation at all. Is it guaranteed to have true rendering/display parity with the OS X variant?