Appalling performance
Yes GUMS,
Performance of big jets is appalling, compared to fighters.
At optimum flight level, at cruise speed, pitch will be around 2 1/2 degrees nose up. For a climb to the next level, once you have burned off enough fuel so that optimum level will have increased by 2.000 ft, you increase thrust (wow, an extra sneeze is all you get) and you "pull up the nose" by about one degree. Of course you will not stall immediately if you pull up steeper, but you will not maintain speed if you do.
If you want to speed up at cruise level, well you will accelerate with about 1 knot per 10 seconds - a long way removed from the 1 second per 10 knots of our previous life!
The margin between high speed red line and low speed red line is not nearly as small as on the U-2, but thrust margin is not big; when you reach cruise level, 1.000 to 1.500 ft/min is all the climb capability that's left.
In the handling of the situation by the pilots of AF447, the biggest communication error, in my opinion, is the talking about "climbing" and "descending" instead of "pitch, check pitch attitude, set pitch 0 degrees".