First of all: I really like Kile, it helps me soo much! Thank you for that. I have a medium size latex project and it already takes multiple minutes to rebuild. If I press the build button, the preview immediately goes blank and then (depending on build steps) I have brief moments where the preview flashes up again and disappears again. This is really quite annoying. Ideally Kile would keep showing me the old PDF until it is completely done with building the new now. It could maybe display a small notification in the preview area that reads "The preview is being rebuilt." or something like that, but it should not hide the preview pane for so long (and intermittent reloading is also useless if it knows that it will perform another build step). Thanks for considering this!
I agree that this is not ideal and could be improved!