Mine is freezing lots now.
First time it went to o2 repair (UK) they claimed they had fixed it, pretty sure they just did a factory reset (which I had done already 3 times). So when I collected it, it froze within 2 minutes.
I'm tracking this repair publicly at http://myo2repair.wordpress.com
so you can check out how this sort of thing pans out.
Problem is it can be intermittent, so you could get a couple of hours without a freeze. So it's gone back to repair and they say no fault found. So a bit stuck now.
It will definitely happen again when it's returned. They say after 3 attempts they will give me a refurb device. Samsung themselves give you a brand new sealed device as a replacement. Recommend going through Samsung if in same predicament.