The food is surprisingly good nowadays at Magic Mountain. I would argue that they have the second best basic counter service food in the LA/OC parks behind Knott's. The pizza is actually good unlike the pizza at Disneyland. Plus, the BBQ is good even if it isn't as good as it is at Knott's. The Johnny Rocket's is also a good option.
I'm as far from a foodie as possible so all the weird and unusual food people like at Disney doesn't appeal to me. From my experience, the basic park food at Magic Mountain is really good, especially when you consider the value you get with a dining pass.
Yes I got a bonus add on for 4.99 a month to the diamond elite membership for the deluxe dining pass so I'd say it's well worth it. All that green food plus 50% off all food purchases. (And merch)