We had a training last week in Redmond, and with the release of Feb CTP bits this week my inbox is being flooded with the question “Should I use the Jan bits or the Feb bits?”

You can tell I used to be a consultant when I say 'Depends'.

Omri Gazitt puts it best when he discusses the trade-off. If you want something closer to the object model that will be released, go Feb CTP. If you want bits that have gone through more quality testing, go with Jan CTP.

Ed Pinto put together a collection of the changes and posted them on WindowsCommication.Net, I'd recommend checking it out and making the right choice based on your specific instance. As the OM is different, existing labs or materials you might be using for training would also need to be updated to work.

Find the list of WCF changes here:
http://windowscommunication.net/collateral/pages/BreakingChangesJanCTPToFebCTP.htm

On the workflow side, Mark Schmidt has a link to the Hands on Labs released with the JanCTP listed with the links to the Feb CTP bits, this meshes with what I'd been told that the Feb CTP would not see big OM changes for WF. 

 If you're looking for the WF labs, find them here