I wonder if you realize that because the Macs have a "tiny market share" (as you describe it) it's just easier (cheaper, too) to produce a re-chromed version of your software rather than writing a completely new interface just for those users.Considering that I wrote that companies might think it's cheaper, I'm going to go with yes, I realize that companies might think it's cheaper.
Likewise, it's also cheaper for PC Manufacturers to sell me junk PCs loaded up with BloatWare, yet I buy Macs. Just as it's perfectly reasonable for company A to make a product that user B finds repellant, it's also perfectly reasonable for a company to make a Mac product that sucks, and it's equally reasonable for a Mac user to avoid it at all costs. Neither party is wrong in any sense, any more than WalMart is wrong for not selling full carbon mountain bikes or Ibis Cycles (a specialty manufacturer who lays their frames up by hand in the USA) is wrong for not rebranding a Chinese steel MTB at a $500 price point.
It's a plus for the users coming from the PC market because they don't have to relearn the interface.
This is not as sound an argument as the one we agree on. Replicating the PC experience with your Mac product works if you have all these PC users at the office and one day IT removes their PCs and replaces them with Macs. Or if you have a company with Macs and PCs and IT support costs show up in a report somewhere, but Mac user frustration with a poor interface is "off balance-sheet."
But if someone owns a PC and decides to switch to a Mac, it's because he explicitly doesn't like the PC experience. Replicate the PC experience on his Mac, and you may find that he switches products as well as computers.