Jax, those lenses are extremely slow. They will most definitely shoot at a slower speed since the AF will take longer to lock on. And while I know my 1D MK IV never really gets 10 FPS unless I hit have the camera in one shot, I can use the AF stop button on my super-telephoto lenses to get the max burst speed. This works great for baseball if you want a shot of the ball leaving the bat. 12 FPS just means that I should get at least 10 in AI-Servo. I also noticed a frame rate increase when I updated my 70-200 f/2.8L IS to the newest version. The 70-200 f/2.8 IS II seems to give me an even faster frame rate than my 300 f/2.8 IS or 200 f/2.0 IS but maybe that is just me.
The buffer should hold around 50 RAW images, the 30 image buffer must have been an early model. Keep in mind we are still dealing with pre-production bodies. Lord knows what is inside those.
People are still comparing the 5D MK III to the 1DX, they are completely different monsters. In my testing I saw only a little more than 1 stop improvement in high ISO with the 5D3 over the 5D2. I've downloaded and played with several 1DX files and they look absolutely phenomenal. The 1DX probably has at least a 3-stop advantage over the 5D2.
This is a great year for Canon and I'm excited to finally get a camera body that combines my favorite features of the full frame bodies with the pro sports bodies. At one point I almost switched to Nikon but this is truly the year the be a Canon shooter. I'm already in love with the radio capabilities of the 600EX-RT.
I know I'm a noob to the forum but here are my credentials 
http://markwebbphoto.com/
I am sorry Mark, but your assumption of 50 RAW files until buffer stops on 1DX is wrong, read my post and watch my video. Buffer stops camera from shooting after 35-36 frames. I wish it was twice as big.
Also, I have tested the 1DX and compared it to my 5D3, 5D2, and the D4, D800,D800E.
No way if the 1DX has a two stop advantage on the 5D3 as you claim, the 1DX has maybe 1/2 stop
advantage on the 5D3. And even if this is good, and just as good as the D4, I was hoping for more from the 1DX. I have lots of RAWs from all cameras, even underexposed to try to lift shadows and check DR in post.
Some beautiful photos at your webpage, great work btw!
