Seriously? Are they so in love with the technologies only available in Leopard that they couldn't make it compatible with Tiger as well?
This is a significant problem on the Mac today -- Apple releases a major new version every one-and-a-half to two years, and developers either (1) have to keep up with the changes or (2) refuse to use technologies that are available across versions, so we end up seeing support for very usable versions of Mac OS X dropping like flies. Yes, it took Microsoft five to six years to release the successor to Windows XP (and it turns out that it stinks), but at least that gives those who choose not to invest in the latest version of Windows viability in the software space.
Apple is guilty of this (iPod, iWork, and iLife requirements, for example), but you'd expect them to push you to the latest version of their OS. You would think that third party developers would make a greater effort to support what was the current version of Mac OS X as recently as September. Then again, this _is_ Intuit we're talking about