I don't have a whole lot of first hand experience with them, which is why I recently was asking about them here. Couple months back I had a Commander railed, only because it was extremely loose. I did not do it for accuracy, and I am not that big on having a super-tight slide to frame fit, which is usually a pretty minor contributor to accuracy -- but this thing was truly so-o loose that otherwise it would not have been suitable for a project gun. I asked the board about Accu-Rails more in the context of breakage and reliability. Got about 50/50 pro-con. It would not be my first choice to rail a carry gun. The rails are very delicate (dropped one several years ago and it broke). I think instances of them breaking in the gun are rare, as in that condition they are not subjected to any side loads, they're well supported. Whatever accuracy enhancement they give would not be needed in anything but a match gun (although I am all for great accuracy in a carry gun). It does make the gun very smooth and very tight, a railed gun feels like a SIG P210!
I have three (Open, Limited and Single Stack) 1911's that are railed. I like rails a lot. They seem to make then gun feel softer/smoother somehow. And when the slide to frame starts to go south, just go up a size of rails.
My STI limited gun has 20K rounds on the past set of rails with no problems. It’s just about time for some new rails.