Nice 3 season tent, inspired by the MSR Hubba Hubba, no doubt. But I took a sharp intake of breath when I saw the price!
Regarding seams - probably stuck together with silicone. But although I have an unsealed seam running along the top of my silnylon tent, I've only ever has a few drips come through (which the solid inner caught) despite being out in some pretty severe weather. Not an issue, in other words, so I don't think that the Vaude tent is a game changer.