I dive the Scubapro mk20-G250Hp setup and here is my opinion about it. The MK20 or MK25 1st Stage (they are pretty much the same. The MK 25 can have the intermediate pressure adjusted externally without a conversion kit.) and a G250HP 2nd Stage. I have the MK/20-G250Hp setup and it has been an excellent regulator for me. I do quite a bit of deep diving (over 100FT), drift diving, and cool water diving and I have never had a problem as far as reliability or in an over breathing situation. I would describe this regulator setup in a few words as: WORKHORSE, RELIABLE, EASY TO SERVICE, and an EASY BREATHER. I have spoken with a few Scubapro techs and they have said that they only major difference between the G250HP and the top of the line S600 is the size. They both use the same service kit.
You will see quite a few people on this board recommend Scubapro, APEKS, and Atomic scuba regulators on this board. All three of these companies provide some of the best scuba regulators in the business.
From my own personal experience with Scubapro, I can tell you that I have nothing but praise for their products, especially the MK/20-G250HP regulator setup.
If you can, try to rent a regulator that you are interested in buying from a LDS. Some LDS will even let you try one in their pool if they have one sp you can get a feel as to how they perform in the water and not just in your hands.