Depends. I had about 1500 blog posts and setting the number of processes to 10 took us about 30 mins.
What if it fails?
Report us and we'll try to fix it.
Any chance of data loss?
Hey! Back up your database before the import. But as far as I know, no. We just read the data from Better Blogs' tables. And if the imported data is wrong, you can always truncate UBS tables just like we did during the developement. That 1.5 version is not a made up number