Being a bit of a klutz, I never get through a framing session without spilling red stuff on mat board. So, for shows in my gallery and the PhotoZone gallery, I choose to frame without glass. If I am showing in a more formal gallery, then I give in to the norm. But everyone I talk to agrees that images look much better without the added reflections.
Certainly, glass protects the image, but in my case it doesn’t matter too much since I print my own work. Cost isn’t the issue if an image shines with a more intimate vibrance.