Yes, I’m using the latest version (2.73). I’m using features that appeared on 2.72 and I’m waiting for the final version of the custom normal editing (2.74, maybe?). So downgrading is not an option.
I have found workarounds for all my error situations. Although the workflow is not smooth (and sometimes forget to do the things in the special way that avoids the failure, making me to repeat the operation), now at least there is a way.
I will wait to see if future improvements/bug fixes in the exporter (blender) or the importer (Unreal) make this process easier. If I found a stopper situation in the future I will let you know. And if the current problems persist in the future… I will try to help looking at the exporter(blender)/importer(unreal) code.
Good luck with the bug hunting!