The Vector Arbiter is a RS optic so it should be quite shock resistant. A colleague of mine mounts his on a 308 rifle without issue. I would say the eye relief is about 3.5 to 4". There is an ever-so-slight magnifcation on the 1X setting but it is not enough to make it difficult to sight with two eyes open. Keep in mind that no zoom scope will ever achieve a true 1X image but the 1X setting on the Arbiter is close. The image clarity is excellent throughout the zoom range.
I got mine during the winter so I haven't gamed it yet. The extent of my testing has been limited to "room clearing" in my house and peeping out my windows.
A thread from a while back discussing 1-4X optics:
http://airsoftcanada.com/showthread.php?t=137817