When Pinkie Pie and Rainbow Dash came to Griffonstone, they had an immediate yet profound impact on the city. The normally stoic and introverted griffons are now, on the whole, a lot more open and amiable. Not all of them, however, are happy that the ponies, who had only been there for a few hours, could change their lives so quickly, and with such little effort on their part.
One griffon learns (through the keen-yet-jaded eyes of their race) how to interpret "the magic of friendship" in their own, unique way.
Note: This is just a short vignette based off of the episode “The Lost Treasure of Griffonstone,” so expect spoilers. Also, as this is my first story on the site (or any site, for that matter), it's partially being posted to gauge feedback, so criticism is always welcome.
You want constructive criticism? Here it is: Do not have all the dialogue in italics. Italics are to be used to draw attention to something or place emphasis on something. Now, if you had three characters talking to each other and one of them made a comment in a language the other two did not know, you could use italics to separate the part that the others don't understand. But since here all the characters were speaking the same language, the italics simply make it hard to read.
I'd say this is a very good first effort. The voice of the main character comes through well in narration and dialogue, as do the other characters. All the descriptions and conversations are good and well paced. The characters are interesting and I like the point that's made about Pony Ways vs Griffon Ways. It's a solid story all around.
Now, as 6013551 said, lose the italics because those do horribly distract here. The rest is good, no massively outstanding Grammer, Spelling, Punctuation issues at all.