I have now had the pleasure of using Flex Builder 3 on all supported operating systems, starting first with the Windows version (XP), then the Linux alpha version (Ubuntu) and now the OSX version on an iMac. Of the three versions, my favourite to use was …
the Windows XP version. It was a very close call between Mac and Windows, but ultimately I found that there was one bug on the Mac version which I really could not work around compared to the XP version. This bug was the “Find” functionality inside the inline help system.
On Windows XP I grew used to well integrated help, which although not perfect was good enough to navigate intuitively. Conversely, on the OSX (10.5 Leopard) version the help seemed to get stuck every time a class reference page was accessed. The Eclipse logo just spins crazily and never seems to stop, thus allowing the search to work.
It may seem harsh to judge the versions this way, especially when the Linux version is only in alpha but if I were to recommend today which platform to use by choice then this factor overwrode all others.
My latest commercial project used AIR and I had the option of using my own antiquated laptop or the brand new 24inch iMac that company had provided. Well, how could I resist the lure of this beautifully crafted piece of hardware and the immaculate look and feel of OSX? Within a few minutes I had installed Flex Builder 3 and was up and running creating an AIR application. It took me a while to adust to using the “apple command” key instead of the “control” key for most of the tasks, but utlimately the only real issue was that the ”apple command” and space (code completion) shortcut was still actually “control” + space. The other combination brings up the searchlight box in the corner which was a little confusing for a Mac newbie. I did not factor this point into my ultimate choice.
Another small and unfair gripe is that the “home” and “end” keys do not work in the same way that Windows and Linux does. The keys will take you to the end and the beginning of the document rather than the current line, which gets frustrating if you are in the middle of the doc – press “end” - and suddenly you have to find your way back to where you were. There are ways to adjust these minor foibles, but as it wasn’t my computer I decided to leave it all as native as possible 
All that said, using the iMac was a thorough pleasure. The compilation speed was pretty much instantaneous (which I expect would be similar on an equally speedy PC) and the BSD command line is so convient to use natively.
The next time I go to choose a new computer for development use I will be hard pushed to go with Windows if I am forced to use Vista. Given the choice, I will probably plum for a Mac with OSX before Vista, but if the Linux version of Flex Bulder 3/4 comes to full fruition the choice will then become very difficult indeed.
So in summary, here is my order of preference for each OS:
- Windows XP (just)
- MacOS X v10.5 Leopard (very close second)
- Windows Vista (dissatisfied reports form others, untested by myself)
- Linux (just because it is still an alpha version)
I am now using Flash Builder 4 on OS X – Snow Leopard. Since version FB4, the issues mentioned in this article regarding the help search have been resolved. Compilation is faster and the experience is generally better, so the new number 1 is OS X for FB4. Well done Adobe and Apple… see you can play nice when it suits you