tl;dr : the hack currently adds about one second to the startup timeYou would also be forcing everyone to have an extra startup delay, not just the few people who might need it.
Just to be clear, we are not talking about a 15 second additional delay or anything like that.
I did some very simple testing on my G10, which has had the "battery door open" hack since its alpha test days.
Using the sweep second hand of my watch, I carefully timed the interval between when I press the "Playback" button and the instant that the CHDK logo disappears, using CHDK builds with and without the boot.c timing hack. Accuracy is at best about 1/2 second and I repeated the test five times for each configuration.
With the boot.c hack inserted, the camera always starts in four seconds. Without that delay, the camera starts in three seconds. So the hack adds
one whole second to the startup time.
Also, as mentioned in the original thread, no attempt was made to optimize (shorten) the delay time. One second seemed to work fine but we could experiment with 3/4 second or 1/2 second. Hardly seems worth the effort although I have read camera reviews that leave you convinced one camera is better than another because of a one second difference in startup time. You never know when that extra delay means you will miss the shot of a lifetime.
Update 1: I cut the delay time in half and the hack still works after multiple startups. So I cut it in half again, and it also worked. At this point, the timing difference between having the hack and not having it is less than 1/4 second. I'd challenge anyone to actually notice that in real life.
Update 2: A little more experimenting indicate things still work with a 1/8 second delay but not with a 1/16 second delay. This may of course vary from camera to camera so a 1/2 second default delay might be wise.
