My 40mm does not have the issue, so I'm certainly not going to update it, not at least until everyone is having the update work well.
I'll keep reading others experiences, but it does not sound good right now.
My 40mm had the issue a few times, so I didn't need to update right away. On the other hand I never had problems with (Canon) camera, iPhone, iPad, router, BIOS or Mac firmware updates which are more complex (I guess). Even my Apple Cinema Display and MacBook Pro battery got updates.
This is my first failed firmware update ever. Lesson learned.