i've just fitted 20 LED7's, took about 2 hours (just fixing the lights in, the holes were drilled previously) which is not bad going i dont think, once you get the hang of the push fit terminals it's dead easy. last kitchen i did was with GU10 cans and LED retrofits and there was 24, and when you have 24 a substantial time is spent unpacking the fitting, removing the halogen, unpacking the LED lamp, fitting it, boxing up the halogen again, then removing the terminal cover , flex grip and slackening the teminal screws so it's ready to fit. with the LED7 it's pretty much ready to fit, you have to remove it from the box, and using a screwdriver it takes 2 seconds to pop off the cover and the flex grip.
as for the hole size, I drilled a test hole at 76mm, and i found that it wasn't very secure in the hole, so decided i'd better follow the manufacturers instructions (71-73mm) and got a new 72mm holesaw. i then drilled 19 more holes and thought no need to check them, the manufacturers instructions will be spot on, but with 72mm holes, it is really tight! they only just go in, i would not like to have to remove one they are that tight. there's no way you'll get them in the hole with 71mm holes, so i don't know why they say that? that said, with 72mm holes they fit spot on once they are in, i've heard reveiws saying the fixing clips are not good enough, but with 72mm holes they are nice and tight and don't move at all. so i think i might try 73mm next time i install some
but the fact that it takes approx 6 minutes as opposed to 15 minutes to fit is a win in my book. i'm never installing downlights with screws on ever again (unless i'm subbing)