FM Advanced is well worth the extra $$$ even if you don't create run time versions of your files. One of the options with it is that you can strip all administrator accounts out of the template copies you put up for sale.
Database files are pretty smoothly cross platform compatible in FileMaker. This is especially true if you design the layouts on a Windows machine. The key difference between the two platforms is that Windows systems require a bit more space, both horizontally and vertically to display the same text. Thus, if you create on the Windows platform, a Mac user rarely has any issues, but if you create on a Mac, you'll need to open the file in windows and make any needed layout adjustments or you may find that some text is clipped or wraps in a way you didn't expect.
There are a few differences between the two platforms that can cause issues. Multiple Window solutions (where you have more than one window open at the same time) can look very different due to how the Windows version puts all FileMaker windows inside an application window.
Bottom line, if you are serious about selling your product and giving it quality support, you really need the ability to test your templates out on both systems to make sure that you have successfully handled issues such as these. If you are running things on a "shoe string" like I am, you may want to find a friend who has the platform you don't have and pay them a visit from time to time to test your system on it.
Thank you for your succinct and honest answer. Think I'll just stick to doing it for Mac only. I don't want my products to look differently nor expecially be constrained by a WINDOWS design parameter !!
Imagine how many hours of tweaking fonts and container size I might have opened myself up for, reviewing all on a borrowed computer.
I am constantly amazed how Corporate Mind can speak lies and especially how easily they do it. ("it will work cross-platform") Soul-less is the concept. Sociopathic is the diagnosis. I weep for the future.
Thank you for the Human Touch. Was a very important deciding factor for me
In addition to the excellent advice from PhilModJunk, may I offer these suggestions:
1) do not discount Windows issues and thereby limit your potential client base; personal feelings aside, there are way more Windows installtions than Mac :)
2) no need to "borrow" a Windows PC; install VMware Fusion on your Mac, then "find" ;) a copy of Windows and install it there; remember that your FMP license alllows you to install both the Mac and Windows version; this is what I did and it works great! :)
3) take advantage of the GO promotion for FMP then just buy the upgrade to FMPA; again, this is what I have done ... you still save :)
The solutions are, from what I have been able to determine, totally cross-platform compatible. Once you toss in the ability to also use the solution using GO on the iPhone/iPod Touch/iPad as well as using IWP (Instant Web Publishing) in any browser on any platform, then you truly have a very versatile and cost effective development environment.