No: 1.7 is not stable and it's not like the current migration situation with South is a particularly large pain-point.
What I'd do is use South now and essentially rebase when you upgrade to 1.7 – ensure that your servers are current with South, remove it and start over with 1.7's built-in migrations.
What I'd do is use South now and essentially rebase when you upgrade to 1.7 – ensure that your servers are current with South, remove it and start over with 1.7's built-in migrations.