I've had a couple of people ask me recently 'Why is the book using the January CTP bits and not the Feb/May/June/July CTP?"

If you're on one of the latest builds, I can imagine waiting for a new code update could be a bit annoying. I wanted to share that I've actually taken a couple days off of work to update and test the the code for the samples I wrote, and I've almost got everything moved over such that they're running fine on the June and July CTP bits. Expect them to be posted here tomorrow. 

 I also feel it's important to provide some insight into how that decision was made to go with the January CTP.

One of the great things about Microsoft is that they’re providing broad access to bits much earlier in the lifecycle, with regular refreshes via Community Technology Previews.  For WCF, Microsoft is releasing drops in CTP form roughly every 1 – 1.5 months. As the product is still in development, the object model has changes each month based on customer feedback (moreso back in November, less so now). Now, of those monthly drops, only a small subset of them are actually allowable for use in production using a ‘go live’ license (per the end user license agreement).  

 There are distinct differences between a CTP that is licensed to ‘go live’ and one that is not. Testing for a ‘Go Live’ release is at a much higher quality bar than a non-Go Live release. The benefit for developers is that they can continue to develop and take advantage of the interim changes much more quickly than in years past (whereas historically, you may have hit a stopping point that of 6 months between a release of a Beta1 and a Beta2) The January CTP ,on which the released code was tested, was the last version that was approved to go into production with a ‘Go Live’ license. The interim drop that followed (February) was not available for Go Live. Based on the information we had, we went with the January CTP, with a commitment to update it – which we’re doing now.

I think you'll find of the authors who've written Beta books, Craig, Nigel, and I are probably the most eager to get updates for the new CTPs out there.