Totally worth the extra cash if like me you tarnish strings in an hour or so! I tested one set whilst in america and they lasted me a couple of weeks, which is unheard of for my acidic fingers (i go through frets like mad too).
I have been using them for a couple months now and i love them. They really do last and still have the great sound you would expect from a set of Slinky's. The coating doesn't affect the tone one bit.
I still use RPS 10s on my JP guitars, but I've got a couple sets of Coated Regular Slinkys I'm going to try out on the 25th. I used the coated Super Slinkys on my wife's Silo. She loves them, especially since she hasn't had to replace them yet.