I've been playing Ibanez guitars with Edge tremolo systems for 25 years and this new light weight arm is a fantastic development. It feels oddly great, stays in place, doesn't wear out the torque bushes as quickly and, best of all, eliminates that unwanted "burrrr" and wobble from the trem's springs when you hit a note hard. With that in mind, the only thing you'll no longer be able to do is that classic Vai-esque flick of the arm to get an exaggerated "burrr", but if you really need to do that just stick the old arm in!
All in all a pricey but highly recommended upgrade.