Considering mac systems only account for about 8% of users you are getting a very slanted view of what things may look like
What are your best practices and how do you check browser compatibility?
I have a PC set up with all the modern browsers (Firefox, Chrome, IE11, Opera) and also an Imac with the latest versions of Safari, Firefox and Chrome and until recently I also had parallels installed which allowed me run versions of IE on the mac for testing if the PC was out of action. If you don't have a spare PC for testing then look at something like parallels for installing windows.
For older versions of IE I have a couple of old laptops with various things installed.
As a quick test for old versions of IE I use IEtester although it is very buggy but does render css with about 99% accuracy.
For testing ipads and iphones I use the mac simulator which is 99.9% accurate.