OS X allows you to format your file system as case-insensitive (the default) or case sensitive (like Linux.) I use case-sensitive, to simplify porting and working on Linux software.
Unfortunately, H&R Block's TaxCut 2008 program won't work if installed on a case-sensitive file system. It fails because it can't find files, probably due to differences between the case of the file name used by the programmer and the actual case of the file name on disk.
A work-around is to use the Disk Utility program to create a case-insensitive image, and install Tax Cut on the image. I used a 600 MB image, so that I can store all my tax forms there too, and eventually burn the whole thing to CD to archive it.