How does that differ from a standard legal agreement? At any time two parties can make a new agreeement, with or without a court battle. Your immutable record is documents filed with the government on public record.
> How does that differ from a standard legal agreement?
> Your immutable record is documents filed with the government
For people who don't necessarily trust the current and future government (to be both just and no inept at keeping accurate records), you've answered your own question.
> on public record.
One of the sales points of blackchain based contracts is that getting your details onto public record, and someone else verifying those details on the records, is easier. And in theory the record is not as easy to corrupt/disrupt/hide/block.
Caveat: I'm not more than an intrigued bystander on the whole blockchain thing ATM, so the details as I understand them may be quite wrong.