SM is awesome! I've only had it 3 or so weeks so I'm still in the honey moon phase but it's a great game. The rules are kinda dumb on paper, shoot the villians until the mode activates, then shoot them some more, but in reality it works great because you always have something to shoot for.
I get to Battle Royal a lot, but never beat the game. The spider sense shot is fun, the vennom shot is really hard, and the doc ock shot is great. The game has wonderful flow, and a really great light show. Adding the shaker motor to this game is a no brainer. I have LEDs in mine and a pinball pro sub. I don't know if I'd do the sub again, but the LEDs look great if you don't mind some ghosting.
I love the art on the cab and I think the back box looks great too. The game is just fun. The flow, the shots, the sounds, the lights, the center post, everything just works.
In terms of the NIB debate, I don't really care either way. Posts, rails, plastic, metal, it's just not that big a deal to me. What is a big deal is the money I saved. I saved $1,200 off NIB and got a $175 shaker motor, $160 worth of LEDs and $99 sub upgrade.
My machine:
http://www.youtube.com/watch?v=NzveTFWK4W8
If you have any specific questions let me know!