I posted this email to wix-users a while ago but the question keeps coming up: "Is it safe to use WiX v3.5?" The next question is always: "What about v3.6?" Interestingly, my answers about picking v3.5 and v3.6 (the WiX builds under development) are very different than my answers were for for WiX v3.0 and WiX v2.0 (when they were under development).
The question started when someone asked whether Visual Studio 2010 shipped using WiX v3.5. I answered:
Visual Studio 2010 (the product) did ship using (an obviously pre-RC build of) WiX v3.5. WiX v3.5 had all the features they wanted and all the features they wanted worked. The next version is already using WiX v3.6. The Visual Studio team is consistently one of our earliest adopters.
Now, instead of being fearful of change (Halloween has passed <smile/>), let's talk about what is changing in WiX and why Visual Studio (and others) are okay picking up new builds.
1. WiX v3.5 is basically WiX v3.0 + Votive for VS2010 + IIS7. That means if you are only using the core toolset (candle, light, dark, lit, etc.) then those tools are nearly identical to WiX v3.0. In fact, I'd argue the WiX v3.5 core toolset is *better* than v3.0 because we've fixed a few bugs that didn't get found until after v3.0 shipped.
1a. Votive for VS2010 - if you need VS2010 integration then WiX v3.5 is the only option. Eric has fixed tons of bugs... many of them in VS2008 integration as well. At this point, I expect that Votive in WiX v3.5 is a better Votive but if you depend on Votive you'll probably want to spend a bit more time verifying it before accepting the drop.
1b. IIS7 - this turned into a large work item as was pretty unstable. If you use the IIS Custom Actions in WiX then you definitely want to spend time verifying the new IIS behavior before taking a new drop.
2. It is pretty rare for features we are not working on to get broken. Sometimes there are integration issues that slip through but typically if your code still compiles, links and installs/uninstalls then chances are you're good.
3. WiX v3.6 is all about Burn. There are changes in the core toolset to support Burn (have to build those Bundles) but they are pretty isolated code paths and I haven't seen regressions in the core due to the additions. That means, except for Burn itself, WiX v3.6 is basically the same as WiX v3.5. Ultimately, if you don't use Votive or IIS or Burn then WiX v3.0, v3.5 and v3.6 are all at almost the same quality level. Given that WiX v3.5 is so close to production, I feel pretty good about using WiX v3.6 myself.
Of course, when taking a new WiX drop you'll want to do some sanity verification to ensure the things that are important for you still work. If they don't, file the bug. <smile/>
To summarize, I actually recommend anyone shipping in the fall of next year or later to consider WiX v3.6. Yep, skip WiX v3.5 and go straight to picking up regular drops of WiX v3.6. As always, if you have questions, I'll happily field them.