[Change from an unconfirmed transaction is available for immediate spend]
It looks like it's going to be necessary to wait for confirmations on your own change from now on.
This is a big deal. If I understand correctly, an entire wallet balance will be unusable until a small outgoing transaction is confirmed?
No it means the entire balance of the change address is unusable until confirmed. The whole wallet balance would only be unusable until confirmed if you only had a coin balance in one address (the change address). Multibit has always been like this because change was always sent back to the sending address. It hasn't done Multibit's popularity any harm.