Hey, I resent that. I would have answered; having said that, I completely missed the fact that the question was addressed to me, until I saw your response.
Anyways. The gallery does stay open in the background...kind of annoying if you ask me. I just don't like apps remaining open in the background. Once the gallery is open, clicking on an image to have it show up full screen takes about a sec for a 'draft' of the image to show up, and another sec for the image to clear up--for a total of about 2 seconds, but it really doesnt feel that long. If your gallery is REALLY closed/exited, hitting the gallery button, takes about 7-8 secs for the gallery to load. If the gallery is sitting in the background, hitting the gallery button, takes 4 seconds for the phone to switch to the gallery AND display the pic full screen.