I've seen lot's of complaints about this on other forums. So I thought I'd give it a try on a trivial test site I have.
It leaves a big security problem too unless you clean up after it. The URL:
www.what-ever-your-site-is.whatever/jupgrade is left with the install directory in place, so anyone can then log in to the (empty) new site.
Interestingly the support links under
all fail with a 404.
Oh well, this is turned out to be a totally useless migration tool.