I've got the high end 13" and no real issues. It's locked up a couple times, but all I had to do was push the power button (to put it to sleep), and press it again, and it resumed where I left off. Takes 3 seconds. I'm sure it's software related. Plus I've had it for a few days, running it non-stop and it's only done it a couple times.
I've also got the 15" haswell, and it hasn't locked up a single time.