This particular beta release is a week late, partly due to myself taking ill last week, but more importantly due to some new work being done in the area of caching, which has proved to be fairly unstable for some users during prior beta releases.
We have high hopes that these fixes will alleviate the number of crashes encountered, however if you do run into a crash please do send in the report that pops up in OmniCrashCatcher, it's very helpful to us.
A number of Visio-related fixes and some other interface changes are also under the hood in beta 5, which should make some folks out there happy.
As always, the release notes and beta download page are at your beck and call.