I've played two games against Bretonnia and I must say that they seem really capable.
My friend was running a 50 wound army with king Louen Leoncoeur, fay enchantress and fewteen Grail Knights against me and I had really hard time cracking those knights with the Sigmarines. I won one game and lost one (in the second game he added a trebuchet that let him kill my Lord-Celestant in one turn with a little help of a single knight poking his remaining wound out with a sword).
Overall it seems very solid as an army.

Maybe they don't have that ridiculous killing blow, but they hit hard and are tough as nails, especially with shield spell from enchantress!
I wonder how viable would be a cavalry-based army of the Empire with Demigryph Knights doing the heavy lifting.
I always wanted a griffon-themed Empire army and now I can have one.
Edit: wheee, 500th post! \o/