I do try
to photograph BIF with my 7D, I say try as I don't go and sit and wait so my technique is already flawed! What I do is stop and take pics when I see birds of prey, my favoured targets.
What I will do though is go to the local seafront regularly and practice, I have hundreds of clicks accounted for by pics of seagulls!
I also attend the Goodwood Revival and first thing I do on arrival is practice on a race I'm not too worried about until my "rusty from last year" technique is refreshed. By doing this I find I get what to me is an acceptable keeper rate.
I think the 7D AF rocks too, I am prepared to admit that the missed and crap shots are me not the camera!
+1 the AF on the 7D totally rocks. I read some stuff about how to tune the AF Servo using C-fn etc to get more out of it. Also, combined with bbf it can be very effective. One thing I will say is the hit rate could be better, but thats what 8fps is for!
For most people 19 cross point AF is enough and for smaller subjects the smaller spot AF mode works well.
Even my 5D2 with its lame AF does OK. Then again I don't shoot BIF or super shallow dof stuff so I guess it depends.