yeah I've heard it a few times. I had the David Willcocks version [Kings college Cambridge] on record way back when and the boys sang the amazing bit of narrative which describes the shepherds in the fields. . . I come out in goosepimples just thinking about it. It's usually sung by the soprano soloist (usually a woman), but on the willcocks recording he uses all the trebles in the choir. I found the section on youtube sung very nicely by a boy soloist, but it has nothing of the excitement and intensity achieved by the choristers under Willcocks. (Couldnt find that version.)
It's been my favourite passage in the whole work ever since.
here it is though -http://www.youtube.com/watch?v=njXIIR4bE0U
its worth a listen I think: Handel at his absolute best. He wrote the whole thing in three weeks and you can tell that he was totally inspired.