It looks like midwestairlines.com is pretty much just for accessing existing FF account information. I booked a flight (at work via our online tool) and can access it on midwestairlines.com but cannot change seats today.

I've called into the toll-free number to check wait times several times this morning and it has been 0-9 minutes on every attempt, so that suggests no mass chaos this morning. MKE is running on-time, too, so it doesn't seem to be a train wreck.