I ordered a kit from them in March, just got it in early November. They told me when I ordered that there would be a long wait, but if you're in a hurry you may be disappointed. They were always responsive when I called them on the phone, never tried emailing them though. No complaints about the quality of the parts, the rifle looks great and is as accurate as I had hoped for.
One of the mags I got with my order was defective; I called them and they told me to send it back and they would send me 2 mags to replace it, which I received within a week. Very satisfied with how they handled that.
One caveat; the company that did their CC processing got hacked and a lot of folks started seeing fraudulent charges after ordering from M1S, myself included (small charges like Itunes,TweetCash and the like). I would hope they have corrected the problem by now but you should be aware.