What if Betelgeuse went supernova and the light reached us tonight?

If Betelgeuse went supernova centuries ago and the light reached us tonight, what would it look like, and would there be any other effects here on earth? If there are other effects, should we worry about them immediately, or would we have time to prepare? If it somehow sends a gamma ray burst in our direction contrary to current expectations, what would that do to the earth and our solar system?