So, before getting into a review of the actual HP Slate, I figured I'd mention how I personally mount it in the cockpit(and car if needed)
RAM Mounts(http://www.ram-mount.com/) are what I have been using for many years for mounting pretty much anything to any other thing. For the HP Slate, and for my Samsung 8.9 Tablet, and for my old Motion CL 900, I've been using the RAM-HOL-TAB-LGU(with some pieces removed for the CL900). This comes with 2 swappable pairs of ends for the different sized tablets.
The more interesting part is the system itself, RAM sells packaged bundles including a tray, ball, arm and yoke clamp. Sometimes, this is enough, but over the years I've flown many different aircraft and needed many more options. So, at present, here's what I generally carry when trying to get setup in a new airplane:
So, that's one long arm, 2 medium arms, 2 short arms, 2 connector barbells and a yoke clamp. And then on the cradle side, there's the standard ball, and an offset ball mount that works better sometimes. Personally, I mount so that the RAM arm is under the yoke, here's the system on the CL900: Chartbundle YouTube CL900 Yoke Mount Once I've gotten the mounting right for a particular airplane I stop carrying quite so many parts.
The most important part with any mount is checking to make sure it's not going to get in the way, so as soon as I attach the yoke clamp, I check clearance, then once the whole thing is assembled with the seat adjusted and my kneeboard on I do a full free and correct check. And once, while inflight to a particularly gusty crosswind landing I unscrewed the arm and tossed the whole thing into my flight bag.
HP Slate 2
So, the other half of this is how does the HP Slate 2 do as a cockpit computer. So, the model I have has no GPS, so there's an adapter off the side(in portrait mode) to the USB GPS I use but no other cables(as I don't have a DC adapter or extra battery yet)
Here's the in-flight(very brief) video: YouTube HP Slate 2 in Cockpit
As you can see, there's one significant problem, while I was flying a plane with a high wing so no sunlight directly fell on the tablet, it did reflect me perfectly. This I'm going to try and make better with an anti-glare protector, which seems better in my outside tests, but will check later in an actual airplane.
The tablet performs fine, if you've used a Windows 7 tablet for aviation, there were no surprises at all, perfectly fine performance with Jeppesen FliteDeck, good touch response, battery was fine for the 3.5 hours I had it on(but I forgot to check how full it was when I got done) The orientation lock switch is a nice touch so that when you turn the yoke to check the controls it doesn't keep flopping the display around. Honestly the biggest annoyance is the position of the USB and dock/power connections(top and bottom center in landscape) which will make cables a bit annoying since I usually fly with tablets in portrait.
The best thing, for me, is the size, it's significantly smaller than the Motion CL900 and fits much better in the planes I fly, less panel blocked and gets in the way less. If I can just work out the screen glare I think it will all be good.