I was at a gunstore yesterday and saw an Aimpoint for sale (NIB).  The model was a Comp M/ML XD (extreme duty).  I went to Aimpoint's website and it was not listed so I assume it was an older model.  Much of this dealer's stock is older because he has been in business for decades.  The price was $319 but I know the shop owner well and usually get a decent discount.  I want to put a dot on my flattop for "urban" scenarios.  Night vision isn't necessary and I don't want magnification. I don't plan on going swimmimg with the gun, but it will get wet on the range from time to time.  The Comp M/ML was matte black and came with a split-ring mount and lens covers.

What are the differences between this model and the newer ones?  Is this one any good or should I shell out the extra bucks for a newer model?

Thank you

You should be able to pick up the newer models... the ML2 or M2... the ML's don't work with night vision devices... for around $330 for the ML2.  The M2's are usually a little bit more.  The XD's are an older sight.  The batteries don't last nearly as long... usually a little bit more than a month if you leave it on.  I sold my XD to a friend of mine last year to get the newer ML2.  I've left mine on the setting halfway to high on continously for 16 months now and it's still going strong.  I'm not sure if I know anyone that's drained a battery yet on the M2's and ML2s.  The only other differce is in the way it's constructed.  I can't remember the exact details, but grabbing the XD's by the bell of the objective and rotating the flip open covers is a no no... something to do with messing up the main tube.  The new ones don't have this problem.