Definitely not region locked.
Has there been confirmation that EU gets the original PAL version vs NTSC for the US? I know box art on the story and the included manual certainly suggests this is the case...
There're been a lot of frame rate complaints with the EU version that the US version doesn't seem to have. The expected cause is that the EU version is the PAL 50hz release being emulated at 60hz thus causing hitches in frame rate. I don't think it's been officially confirmed that this is the case yet though. It's just the explanation that seems to make the most sense.