It actually makes logical sense for Gengar to not have levitate since its clearly not levitating. Course it seems a bit odd to try to make Gengar of all pokemon more logical.
Then again, I never used Gengar so this change doesn't effect me much, and I'm pretty sure it is still a great pokemon and great Mega.
On another note, a lot of crazy or surprising new pokedex entries for new and old pokemon. Sharpedo gets a conservation themed one related to shark finning! I'm all in favor of that but its still surprising.
Getting dex entries for all the different forms and mega evolutions is also a welcome change.