Snow Leopard (Mac OS X 10.6) is out and Sente seems to be handling it just fine. We have had no reports of problems related to the Mac OS X update.
One improvement worth noting that comes along as part of the Snow Leopard upgrade is that selection of text within multi-column PDFs is much improved. If you run Sente under Snow Leopard, you will find that selecting text from one column in a multi-column PDF now works the way you thought should have worked before. Hats off to Apple on this one.