It definitely is, and I'd highly recommend them. Sprite (member here) has had them do services on his car. Contact Ed Bolian there...great sales guy. My GF bought a G63 from him and it couldn't have been easier.
I was looking at used 12C's a couple of months ago. As negotiations got underway, it was clear they couldn't touch the deals other McLaren dealers were offering (both on the 12C and my trade). I ended up buying from Park Place in Dallas. As far as service goes, it's been a little bit of a mixed bag for me. Luckily, I haven't had to have much done. I got the P13 update without incident. I also asked them to look at an issue I'd been having with the swipe doors (I have the double swipe problem others in this forum have mentioned). They investigated and determined this was "normal" since other cars on their lot did the same thing. At my next service, I'll push harder on getting that resolved. Anyway, certainly there's no question in my mind they are a full-fledged McLaren dealer and you shouldn't hesitate to put them in the mix as you are shopping around.