The guides at the moment are horrible (granted I don't use them much for most of my work but on the job I have at the moment they are proving quite critical for making accurate masks on shape layers. The three pixel width lines are truly horrible and just make them look like a blurred line. Please just revert back to standard 1 pixel width lines - that is fairly essential for accurately placing them against objects on a visual. Or, if that is an problem for retina screens (which I'm thinking may be the reason they are like they are), then please put an option in the preferences to revert back to a single pixel line.