I will be migrating to DNN 4 in 4 to 6 weeks. I am holding off to see how 4.1 is.
I have been testing for some time now, and DNN 4 seems the way to go. No comaptibility issues as of yet.
We will be migrating to 4.x within the next 6 months.
Everything currently running on 3.2 but I am in the middle of working through upgrades to get everyone up to 4.3 within the next few weeks as well.
Clem