I can understand that, but there are two reasons I'm not stressing over it for my own purposes. First, the MX-700's core architecture appears to have carried over into the latest models (the MX-800 and MX-850) almost unchanged - same features, same configuration software, same config files - suggesting that the life span for that core isn't over yet and that support for it should be reliable for some time to come. Second, I've read some comments indicating that both the MX-500 and MX-700 have undergone some design tweaks and improvements throughout their production lives (the move to the "gemstone" button finish on the MX-500's being probably the most readily apparent example), which means that a newly-manufactured MX-700 would lack very little on the 850. Not to say that there's anything wrong with the 850 - the RF ability and improved thumbpad are both potentially significant, depending on the user - but I don't think the 700 is going away anytime soon.

I'm surprised that the SMS-1 gave your MX-500 trouble - it's basically the same UEI remote platform (albeit simplified) as the Catalyst48 used by the 990 and the 1070/970 (and the 1050 before them all). There shouldn't be anything out of the ordinary about the IR commands that I am aware of.