Hello?
I don't know which version of Merriam-Webster you looked at, but that is the EXACT dictionary I've repeatedly quoted which says it's acceptable and in fact common usage in business and journalism and fiction writing.
So get over yourself, you twit.
http://www.m-w.com/dictionary/alright
M-W online is a collegiate dictionary, btw and pretty good for everyday stuff. However, for formal writing or scholarly work you should refer to an unabridged. I cited Web 2 unabridged, which is a lot more authoritative. Same company.