Apparently in early July, there will be several dozen opportunities to observe first hand the issues related to weblog migration. For those unaware of the why's and wherefore's, I recommend that you start here.
A few relatively safe predictions: some of those who didn't much care about "unusual character" and escaping issues will suddenly get religion. And some of those who are devoutly religious about well-formedness will find the temptation to use a regular expression or equivalent technique necessary to scavenge what data can be salvaged and succumb to the temptation.
However, this is not a time for religious debate or partisanship. It is a time for compassion and an opportunity to learn and improve. Enough so that I am willing to step forward and offer to help with writing of conversion and migration tools. Assuming that the input looks anything like this format, I am willing to write conversion tools to either a comparable format or to a blosxom's directory layout.
Including this format. As I said, this is not a time for partisanship.
This is something I know a little something about. And I want to help.
One thing that would help me now is an example roughly approximating what of one of the exports that will be produced in July will look like.
My recommendations to anybody who is considering a move, first take a close look at the export capabilities of the intended destination. Make sure that it is something that you can automate and place the results off site. Also, strongly consider getting your own domain. These two considerations outweigh any choice of tool, IMHO.