Recently I went through this exercise, so I thought it might be helpful for others if I post about it.
First advice: don't try it - it doesn't work. The process starts, but after a while stops and it just hangs on, hangs on... never gets done.
Workaround. Installed Mingus 1.2.1 and the script works as a charm. Imports correctly all the posts and comments. The only thing it didn't bring over correctly: the popup images.
After that I did the famous one click update to 1.5 and now it works perfectly.
Hope this could be useful for other "importers"...