I also got to spend some time working with various and sundry Web browsers today, to wit:
Mozilla 1.0.something on Mac OS X and Windows XP
Netscape 7.something on Mac OS X and Windows XP
IE 5.something on Mac OS X
Netscape 4.8 on Windows XP
On Mac OS X, yup, it's true, Safari is the fastest, but only slightly faster than IE. Mozilla/NS7 are still slow as hell. My big problem today was that IE couldn't handle non-Western characters in the title bar, which is ugly but not strictly necessary. All in all, Safari is by far the least complete of the three, but don't worry, speed will probably suffer just as soon as they start adding other features. Biggest Safari complaint: the weird way it uses the Address/Location bar as a progress meter. Bleah. That blows. It also has an annoying way of not providing any feedback to user interaction - it just suddenly displays the new page. Mozilla is still the lamest by far, although its plethora of "bonus features" are vaguely compelling [although not as nicely implemented as MSN Messenger for XP; I don't know about the OS X version of that]. IE seems to be as good as you could reasonably expect it to be.
Favorite dialog box of the day: Acrobat Reader spouting off something along the lines of "You are currently configured to use Acrobat Reader to view files of type .PDF. If you would like to discontinue using Acrobat Reader and start using Acrobat Reader instead to view these files, tick OK". [I forgot exactly what it said.] V. odd. I guess there's some weirdness when PDF files are also OS native files.
On Windows, my big complaint today is that IE doesn't deal well with "view-source:URI". Mozilla/NS7/Nav 4.8 all display non-Western files perfectly; IE craps out. Ha ha! Finally, a reason to use 4.8: NS7 is broken in that you can't save the Unicode pages to disk - if you do, it barfs out regular ASCII and it will never display correctly again. 4.8 can't save it at all, so you're kind of hosed that way too. There doesn't appear to be an easy way to view Unicode source and save it without copying 'n pasting to Notepad and being careful to save as Unicode.
Didn't try Opera or iCab, but I don't have all day.
Ultimately, it looks like "officially supported browser" for the funky XML/XSLT stuff in future FileMaker is still TBD.
Man, you'd think they'd have sorted out browsers at this point in history, but I guess it's still an open field.