There was some confusion on December 5th when Bob provided highlights for the WiX toolset "beta exit" build. I saw a number of people declaring the WiX toolset finally "in beta". That's not quite right. The WiX toolset was in beta for all of last year as we worked through the feature set and quality bar. As 2008 came to a close it felt like WiX v3 was a solid improvement over WiX v2 and the quality markedly improved.
Now the WiX toolset is in "release candidate" mode. Release candidate is a term made up at Microsoft to describe software that is accepting fewer and fewer changes. I think it is easiest to define release candidate in contrast to beta. During the beta period you are looking for feedback on feature set and overall completeness of the software. During the release candidate period you are fixing bugs to finish the software project.
Finishing is an important and often difficult process in software. Each change you make has the ability to break already working functionality or expose even less desirable behavior. At some point in time you have to choose to fix bugs in the next release and declare this one done.
That's what we are starting to do with the WiX toolset now. Adding MSI 5.0 support to WiX was completed later than we would have liked but we were dependent on the release of the new MSI SDK. Similarly the Visual Studio team has promised support for Votive in the next version of Visual Studio and that functionality will be coming in late.
However, we are going to start punting bugs to the next version of the WiX toolset. Remember the WiX toolset is not in beta any more. We are on the glide path to shipping.