Wanted to share some findings regarding installation of new version on Win10/64. I was using previous version and was excited to get new supposedly much faster/multithreaded … After installation I would say it was even slower than previous one, but … I found culprit.
In order to be able to use previous version I had to setup compatibility to Win8 to avoid constant crashes. And after installation of new version that setting was retained and new synfig was still using single core 
So please make sure that after install you remove that option - if you used it. I’m pretty sure a lot of people on Win10 felt into same trap - hope will save some time for others. And I think setup should check for that option and at least warn user if not reset it automatically.
First of all I have found bugs that totally disqualify 1.2.0 version - discussed that in thread [url]Distortion/twirl and other filter layers problem - bug] - also filed a bug on github.
Since have to finish project by Wednesday and 1.2.0 is useless started exploring other options. And I was pleasantly surprised to find solution which works much better on windows.
Since 1.0.2 does not work as multi-threaded app on win it is excruciating slow to render anything. So the only option left was to try linux version - but as all win users do not want to mess with dual boot and all that mess - so I tried VirtualBox with guest ubuntu 16.04 and linux synfig version 1.0.2.
To my big surprise final render performance was almost same as 1.2.0 multi-threaded on Win10 despite VitualBox was using only half of my i7 memory and threads.
My conclusion here would be that it is not worth to try win versions at all - just install free VirtualBox, set it to use all possible resources, install Ubuntu and run Synfig 1.0.2 on it.
Of course you will feel some delays but they are not much worst than on windows when working on complex project.
For ease of use also utilized VirtualBox shared folders (some more linux messing to properly set permissions - all info found on inet) so I could easily and immediately use synfig render output with my windows tools…