The Bonds of Evolution! serves as an introduction to the Kalos Champion (and famous actress), Diantha, and gives a more in-depth look into Mega Evolution. We get a couple of extremely one-sided battles along the way, displaying the intense bond between Diantha and her Gardveoir; she doesn't even need to Mega Evolve it to dominate against Ash's Pikachu.
I gotta say, even though it makes sense in its own way, the whole "strong bond" stuff is kind of lame. I mean, how many times does the show need to throw in our faces that "Trainer's and Pokemon's hearts must be united as one"--it gets a bit silly to a point. We're probably gonna be hearing it another thousand times before the saga is over. Mega Evolution is cool, and it is definitely going to be a key feature of the XY saga--as it should be--but we're definitely gonna have to take those "strong bond/hearts united as one" lumps along the way.
Diantha is quite likable, and we'll definitely be seeing her again. Team Rocket, by contrast, is (again) totally unlikable and unentertaining, but we will surely be seeing them many, many, many...many, many, many more times. Oh well, thems the breaks.
Grade: C-
Side Note: There was possible foreshadowing of Ash winning the Kalos League and facing off against Diantha again. Let's hope that comes to fruition.