SyncToy 2.1 is not only very slow, but it trashes things if interrupted in the middle

Question

Here's my situation:  I want to use SyncToy to sync a folder between two machines with about 100GB in 100,000 files.  Most of the time, there are very few changes to be found.

It takes SyncToy well over a day to complete its preview the first time I run it.  After that, it's usually acceptably fast--maybe 10-15 minutes if there are only a handful of changes.

However--and this is a big however--if during those 10-15 minutes I stop the synchronization for any reason, then the next time I start it up, the results are just plain wrong.  So I have to blow away the folder pairs and start again from scratch, again taking an entire day to set up the databases.

Is there a better way to solve this problem?  Is there a SyncToy 2.2 in the works that might avoid these performance problems?