It's going to be a great system for those who use it. It's FastPass, but with less users, so it will be more effective.
Of course, if everyone uses it then it will just be the same old FastPass but now costing money. We'll have to see how it plays out.
I think it will be better at Disneyland. FastPass works better when you have more attractions to choose from, improving availability. It's also more heavily visited by locals who may be less likely to shell out a daily fee.
How the rules and tiers work will factor into value. The last time I went to Disney Studios I could only get a Slinky FastPass late in the day. As a result, I never got more than my three FastPasses that day. With a paid system, if the primary pass I want is only available later in the day, I don't want to be restricted from getting other less popular ones throughout the day.