First of all, I have the i7 256 and the machine is great, I hope you go ahead with your purchase if you are interested in this kind of devices! I can confirm what the other say: with light use, the machine is just pleasantly warm (not more than your skin). If you do heavy work (or stay for a long time on some crappy webpage with inefficient Flash components), it will get warmer and eventually very hot, but even then, nothing suggests that this is not by design and that it is going to fail. Performance stays quite good even under these conditions, you will only notice the difference if you are doing heavy gaming, video conversion, file compression or so. As other people said in this forum, this is "running hot", not "overheating". After you are done, or you close the crappy page, in 2 to 5 minutes you will be back to the previous temperature and the fan will stop.
Oh, and I never had any thermal shutdown, and nobody has been reporting them for quite a while now.
The problem seems fixed.
My two cents about the model to buy are that the price difference between the i7 256 and the i7 512 is unjustified. Come on, it's about 400 € (or $) difference! I guess everybody here know that SSDs are expensive, but how much can the cost difference between a 256 and a 512 GB SSD be? I would suspect around 100 or maybe 150 $, and I understand that they have to earn on that difference, but 400 €/$ is definitely excessive.
I would have liked the extra space, but I got the i7 256. I really had the feeling that they set the price so high just to get money for the kind of people for whom money is not a problem and who can afford the best model regardless of the price. I could have put the money for the i7 512, and probably I would if, for that price, they had included some more goodies, so that I could have justified the price to myself. With those 400 € I can buy as much as external storage as I need, and I believe that most people (including me), despite having more than 256 GB of data, don't really need to access all of it at SSD speed.