Actually, I can probably live with this. As long as I can SB for free with cabin space available, it should probably be okay. Getting rid of the change having to be done within three hours might actually be a positive, and I usually SDC to the next earlier flight, which is usually within 3 hours. If there isn't a flight within 3 hours, I'll weigh my SB options.
For those of you upset about people who change flights getting UGs, this may alleviate part of the problem. SB does not get on the UG list until after clearing the SB list, and the UG list is often cleared before the SB list.
I'm not happy about the required same-route restriction, but I'll keep my fingers crossed that this can be waived from time-to-time, much like they allow me to fly into GSO instead of RDU or PBI instead of MIA already.