I have had lots of experience with buffers, and personally, I think the only time you should use one is when your car is really scratched and has years and years of swirl marks.
They do work well polishing the car, yes--but the kinds I've used range from cheap plastic ones, to heavy metal ones, to $500+ industrial 1800 rpm, and I really can't say I've had success with any of them unless the car has rough areas, areas with tar or bugs, light scratches, or swirls.
My best advice would be to buy diamond shield wax (but there are MANY other brands of wax and polish
http://www.e90post.com/forums/forumdisplay.php?f=13). Cut up a 100% cotton tee shirt into a small piece (make sure the small piece is wet, large piece is dry) and large piece. Use the small piece to apply the wax, use the large piece to take off the wax by hand, in straight movements--both applying and taking off. Never apply or take off the wax in direct sunlight. I think you'll be surprised how well old fashoned elbow grease works on a new
finish
EDIT: Oh, I forgot to mention, a buffer will put very fine scratches in the finish, no matter what kind of buffer or wax you use. However, buffers usually cause clouding or swirl marks, especially on jet black. On other colors, it would be more difficult to notice. But if you are looking for a genuine glass look for at least a year or two (before your finish gets naturally weathered), do it by hand.