While I don't run Mac, I do run Linux and I use a VM of Windows (actually I run VMs of Windows from Win 98 to 8.1) via Virtualbox.
No hiccups, however, you must make sure that your machine is capable for essentially running 2 OSs at the same time. That's going to be the key thing as to rather or not you have a good experience with it or not.
I tend to also suggest using "shared folders" to get files in and out of the Windows side of things and deny internet entirely to Windows.
I would suggest getting an anti-virus/malware for your Mac.
1. Even if you get a file that has a Windows virus to your Mac and it doesn't affect your Mac, it could infect the Windows side of things. Which would be no bueno.
and
2. Contrary to popular opinion, Macs (or any OS connected to the internet) needs to have this protection. Even Linux with just barely over 2% of the desktop market has viruses/malware written for it.
When running a VM (or even dual booting), the OS and programs don't know that it's in a virtual environment (when dual booting, they are actually installed directly on the hardware as well). So for all intents and purposes, they are all running in a Windows environment.
However, I wouldn't expect support from the software company when running in a virtual environment as more then likely, they may blame it on the hyper visor software that you are running or at least as a variable that they couldn't rule out if you have an issue. I can actually understand that issue. May not be fun if you do have a problem, but I can certainly understand their stance. I know Wilcom will not support the software running in a virtual environment and the full version of that costs a whole lot more then the full version of Flexi. So just keep that in mind.