Closing for moment awaiting more infos from https://connect.microsoft.com/VisualStudio/feedback/details/630350/threadlocal-documentation-and-actual-behavior-mismatch

Fair does, the documentation is a bit ambiguous, and I've resisted the urge to go and reflect it and break the terms of contribution so can't tell for sure what is supposed to happen.

I'll need to keep an eye on this though as it's keeping a project I'm trying to get functional from working - I have a workaround but I am trying to not change any code in order to get it working on Mono (As I shouldn't have to)

A simple workaround to get the same behavior on both Mono and .NET is to explicitly pass () => default(T) factory lambda in ThreadLocal constructor (putting it as a reference)

Aye, for now I'm going to keep running off this 'fixed' version in hope that a +ve remark comes back from connect, I'll have a dozen more by the end of the week anyway with this project I think :)