From what I see on that site it looks like a great idea for the obese and if it works as described it would be a good option to make it available on the NHS for selected patients of course.
I think the problem with it could be that it would be abused by some. I eat a lot, but fortunately I don't have a big issue with weight, maybe could do with losing 3 stone. With that device, I could just carry on eating vast quantities and suck it back out again without the need to diet. From that point of view it could be easily abused, with little incentive to diet. So once all that food has been sucked out, wouldn't you then be hungry again, now having a nearly empty stomach?