IMHO (as a long time user of OO.o and LO), the biggest issue that libreoffice has in 'interfacing with its users' is in the many rendering bugs and unexpected behaviors (frequent crashes of java code for instance) that are so unpredictable and unrepeatable that do not even get reported.
So, making an effort at improving the 'user interface skin' of the application is OK only if it does not get in the way of the real bug fixing or taking away all resources from that.
Would be at best 'weird' to wait two years to have an all new looking LibO, still incapable of doing impress animation properly on linux, or doing wrong font rendering when graphics acceleration is on, or incapable to have 'inline' (anchored as character) math objects in impress and draw, or starting up with a wrong looking splash screen (again on linux) just to mention the first few things that come to my mind.
Otherwise, if the UI overhaul can go on without disrupting normal progress in these areas, it can certainly be an interesting effort.