I've always taken it at night because once in holland I really messed up and took 2 yellow microdots in the car on the way to work in a tulip packing factory, big mistake. All those tulips lol.
But recently I did try it at dawn and it was a great day, and by evening it was all over and i had a normal nights sleep, so it didn't feel like I had wrecked my body clock or anything like that.
Also, I have always done lsd with heaps of weed handy, but this last time tripping in the day i purposely didn'y have any weed around (as an experiment), I found the trip very very different, not nearly as many visuals, It was strong acid and was definately kicking my butt nicely, but somehow the lack of weed made it very cleaner and more focussed, and I think that maybe the comedown and after affects that I have always felt (like totally exhausted afterwards) probably came from the fact that I had just been puffing huge spliffs for 12 hours straight as this time without the weed I didnt feel so fucked up afterwards at all.
Dunno what to think really, I do like my weed and I did miss the visuals, but was still a pretty cool experience.