You can always sign up with AT&T without a contract, this was the case as always. THere wasn't a benefit however because you paid the same price as if you had a contract.
With T-Mobile - you pay less per month than people that have a contract if you buy your phone full price.
For me, i save so much money per year ($700-900) that I can afford to buy a new phone every year without even thinking about it.
My plan on AT&T used to cost my $110/month (+ taxes/fees), now I pay $50 (taxes included) for MORE than I had before (get international calls now included