Back from the dead, I personally think the action is a good change. Here are my reasons:
1) Action was brought about at a good pace, not too fast, allowing a transition.
2) Transition allows the manga to become serious and move towards a proper ending.
3) Action is not brainless action, characters have respectable strengths that do not involve "hollow"/"nine-tails" ---> outside UNBELIEVABLE power.
4) I believe that this arc is also meant to raise Negi's level to finally match Fate.
5) We go ever closer to the truth about the war and Negi's mother (if Negi wins) and even if he dosent, he still needs to face Fate.
Although I do have to admit I prefer the Chao arc the best and most interesting...