It seems likely that alright will one day become an accepted form of all right, but that day hasn’t come yet. So in the meantime, stick with the standard whenever your writing calls for it, and you’ll be all right.

We do, however, make an exception for Matthew McConaughey.

http://pandawhale.com/post/38514/matthew-mcconaughey-alright-alright-alright-gif

More on the subject of alright:

http://pandawhale.com/post/50925/its-all-right-to-use-alright-britannica-blog