[Ken Case]

OmniGraffle 4 still works on 10.4, and we'll give a free OmniGraffle 4 license to anyone who buys OmniGraffle 5 but needs to be able to run OmniGraffle on 10.4. (Of course, in your case you already have an OmniGraffle 4 license.)

So why did we choose to go Leopard-only? There are lots of significant new developer features in Leopard that make our developers more efficient, such as the first major update to Objective C in over fifteen years. Taking advantage of those Leopard-only features makes the application run faster and saves us time in writing it; but taking advantage of those features means that, unfortunately, it no longer runs on Tiger. We had to decide whether we wanted OmniGraffle 5 to have more improvements (more efficient developers means we have more time to improve it—and, of course, leveraging Leopard features means we get some improvements that are otherwise impossible) or to be a more compatible product, and for OmniGraffle 5 we chose to make more improvements.

(We made the opposite choice for OmniFocus 1.0, much to the disappointment of our development team on that product. But in OmniFocus' case we didn't have an earlier Tiger-compatible version we could give our customers, and we wanted OmniFocus to be available to people who hadn't yet made the switch to Leopard.)

Make sense?