The S800 (8 arm UAV) is a great photo platform, but can get pricey and is heavy. There is a Hexacopter (6-arm) copy on Ebay similar to the one Flir recommends http://www.ebay.com/itm/201020037443?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 , you will want a bigger gimbal if your using your Thermal Imager - and plan on buying extra batteries and a quick charger. If anyone is interested, contact Todd and tell him Mark @ Allsite sent you.
The DJI Phantom II is better than its predecessor, but will still require video editing to remove Jello effect or vibration. Accessories and parts are expensive for what your actually getting - but it does look cool if you customize it a bit.
In my experience Quadcopters are not as stable. Your better off getting a custom made Tricopter Y6 - dual motors per arm. The coaxial design increases the gyroscopic forces exerted on the frame, thus resisting outside forces better than if all the props were spinning on the same plane, it allows for a much more stable platform than a quad setup, and if a motor fries, your still able to limp the guy down instead of experiencing a free fall landing. With 3 arms instead of 4, your using less parts = less weight = more flytime.
I should get around 15min + with camera and Im at 7000ft, which requires around 20% more power consumption.
If your using a GoPro setup, spend the extra $ and Get the Hero3+ Black edition - its smaller and has faster Wifi. I had to adjust the focus on mine, its pretty easy and there are plenty of You tube videos on how to do it.
I have the same guy building a Y6 Tricopter and Crawler setup for me right now. Should have them next week. Ill post more pics once I get everything.
Here it is in progress: