For years I refused to pay the extra money to get an Atomic regulator, but I finally gave in and purchased one about a year ago. I must say, I love it! Of course, it hasn't been up for servicing yet...so we'll see what happens there. Either way, I think it was well worth it. I have about 10 different regulators now (I'm one of those types of guys you keep borrowing gear from, cause all my friends borrow from me) and have owned somewhere around 20 regulators and I can't think of one that breathed easier than my Atomic.
I know when I purchased my Atomic, I had lifetime warranty for parts. Not sure if they all come with it or if just the recent models, but that is one of the main reasons I gave in. If the warranty is transferable then that might be worth it alone.
Either way, I have used all 3 of those regulators and liked them. I can't speak much about the price you'd pay. I've only bought new regulators (Don't like not knowing what the previous guy did with the regulator that is keeping me breathing at 120 feet). But taking it to the dive shop for servicing and testing would mitigate that, but I’m still not much of a used life support stuff.