I just used 845 for the first time on a Mustang w/a fresh, single stage paint job and I'm a total believer now. The shine is simply amazing, and considering how easy it was to apply and remove (being conscious of the "thin" rule), this will now be my go-to wax for all my vehicles.
Though I can't offer a comparison vs the other Collinite waxes, I find it difficult to believe anybody could go wrong w/845. Perhaps, if my vehicles were parked outside, I might go w/476 or 915 (probably based upon a wrong belief that paste waxes are superior to liquid ones). But then again, 845 isn't like a regular liquid wax...you definitely have to warm the bottle and liquefy it prior to application (not to mention, constantly shake the bottle for good mixture). When sparingly applied w/a DA buffer and buffed w/basic microfiber towels, it's a breeze.
BTW: Many of the detailer websites sell it for $16-18/bottle, but then tack $5-7 shipping on top of that. There are a few guys selling it on Ebay w/free shipping for $16. Considering you'll only use 2oz or so per vehicle (unless we're talking huge truck or large SUV), it's a bargain.
M_C