Yeah, I hate that. The contracts program we use here requires ActiveX, which is IE-only. Top Producer is also Windows only.
If I want to use a Mac in the real estate world, I have to pay more (only wireless card-capable laptop is the MacBook Pro and I have to install Parallels + OEM Windows).
But whatever, it's worth it. Using a Mac makes me stand out from 99.9% of the Realtors out there, including the 95% who are hesitant to embrace technology. I can still use Pages, iPhoto, iDVD, etc.
I'll start saving up for it.