The ST is not, by nature, compatible with the Mac. In fact, it is (on
the surface) more compatible with the IBM computers, because it uses the
same floppy disk format.
However, inside the ST is very similar to the Mac. Several companies
have offered hardware additions to the ST or Megas which allow them to
run Mac software. I've heard that the best is Spectre 128, which runs
Hypercard, Adobe Illustrator, etc. It actually uses a Mac 128k ROM, so
it is very compatible.
If you want to use Mac disks, however, you will have to buy a special
converter box for your disk drive, which will cost a couple more
In the end, take a close look at the software available for the ST
itself. It is often as good or better (I've used the Mac too), and
tends to cost half or a third as much, like the ST.
* Via ProDoor 3.0R