Sitefinity works on Mac, actually. There are customers, who use Sitefinity on Mac and they manage to complete their tasks pretty well, despite the fact we don't target Mac browsers. The only concern is that some css elements don't look like the ones on IE and FF in Windows, for example in edit page mode Edit
buttons are in 2 rows, but I guess this is not a important issue for you. You can test the admin in our demo site
We actually plan to improve our browser compatibility.
the Telerik team