I spent a year on the unreal 2 editor many years ago which was fun. The unreal 3 editor - come UDK a few years later was awesome and I have spent a few years in UDK, as a solo dev there was a lot to learn in UDK for every aspect of the development of my games.
After using Unreal 4 for 2 weeks, WOW! Everything is so much easier, even down to assigning some player input. The blueprint system is a godsend for me as I am an artists at heart and although i have learned a lot from unrealscript and accomplished many things, Blueprints are much more user friendly for an artist.
As with all good feedback, there should also be some negative so you guys at EPIC don’t all get big heads and cant fit in the same office anymore. So my only drawback is the amount of crashes i have had. This is alleviated somewhat from the awesome auto-save feature which is essential for me.
Great Job I look forward to producing something Epic with U4