WWDC has come and past, and we're all back and situated back home, and have another beta release for you all.
On a rather important note, it turns out that the beta 3 release had a nasty Unique Graphic ID bug in it, as a matter of fact it wound up getting fixed on the couches or bean bag chairs of Moscone West last week (or in that general vicinity). So, if you were using OmniGraffle 5.0.1 beta 3 then I encourage you to get this release.
We've fixed a few other annoyances as well, you can read the release notes at the venerable OmniGraffle beta page.
Cheers!