Slipstick features a comprehensive article detailing the latest known issues that people encounter while testing Outlook 2007 Beta 2. The most common problems I hear about are caused by incompatible add-ins which can be disabled in the new Tools > Trust Center window. If Outlook crashes while you are trying to disable an add-in (this is known as Sod's Law) you can edit the Load Behaviour for questionable add-ins in the registry at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Outlook\Addins. Change the Load Behaviour value from 3 (active) to 2 (inactive). Any add-ins you see with a load behaviour of 9 have already been fully disabled.
Disclaimer Thingy: As always, Beta software should only be used for testing purposes and I don't recommend you use this on a production computer (i.e. a PC that you rely on!). Here at Microsoft we "eat our own dogfood" and experience firsthand the joys of using pre-release software on our day-to-day work machines. Having tens of thousands of colleagues complaining about a not-yet-perfect feature provides a pretty compelling incentive to the developers to fix things fast! Oh, and editing the registry should only be done if you really know what you're doing and have the necessary safety net (i.e. a backup) and protective underwear in place.