Google did something interesting with this, they do real-time lookups into the ie store as users visit sites (the uri is the decryption key) and migrate if data is found and decrypted successfully. If the overhead isn't too bad (maybe we can get a copy of the site list to key off of?) we might try something like this. It doesn't fit with our current all-or-nothing approach, but if users find it useful we might consider it.

Not being able to bring your passwords to Firefox seems like a good reason not to switch to us.