Of course it's buggy!! UV mapping is a horror! You cannot save it. you have to complete it all in one go!!
All of my exported objects develop a new material zone on export.
I'm pretty sure there is a memory leak.... It works better every time I upgrade my machine!!
It ignores the scale you set in the export dialog. Just pretend you don't see the option, Hex doesn't see it either!!!

On the plus side, it's cheap, it works. You can make pretty cool stuff. It will let you create greater than 4 sided polys, but it will tell ya where they are if you ask.
I've got Silo, too, but I need to spend more time with the Tutorials!! Silo doesn't like to make triangles, but it will UV map reasonably well!

;>

Andy!