Note it's FontLab Studio 5. The release is coming closer. The application is very stable now, has some minor issues to clean up. We are intensely working on the new manual. I'd say 4-8 weeks.
One of minor issues that creats major problems is that OT kerning for rtl is done in the wrong direction. (with 4.6)
If it's not dealt with yet, you have 4-8 weeks! According to a programmer friend who wrote a little program for me to fix it, this is easy to fix.