Hi folks,
tl;dr - Use 4.1 unless you have a good reason to use 5.0, which will be out much later than 4.1.
Recently, we have been focusing our effort in our new branch '4.1`. It is API-compatible successor of 4.0, which means recompiling your 4.0-based application against 4.1 will not introduce a regression (hopefully!)
So, what's the difference between 4.1 and 5.0? It's not much. We backported most of interesting features already.
There are only three features that were not backported so far:
* Removal of deregistration - unable to backport since it will break API compatibility.
* Simplified handler type hierarchy - unable to backport since it's API change
* More flexible thread model - trying to backport it.
Unless you want the features that are not going to be backported, I'd recommend you to stick to 4.1.
Thanks,
T