Ya know, I'm sure this is going to be the boilerplate answer, but this is what I've found with wahs:
DISCLAIMER: I just took a tramadol for my back, so I'm a bit tangential with my thoughts, at the moment.
I've tried the Silver Machine through different amps, different guitars, different pickups blah blah blah. I liked how it sounded, I liked the features, but (and I find this with every wah) to get that "wah tone in your head" you gotta match the right pieces of gear together. For me, I HATE the sound of almost any wah with active pickups. I don't know why, but the only wah I've liked with active pickups is my Vox 847. Also, in live and studio situations (this may go without saying) I have found to get a great wah tone, you have to find the perfect mic position...live this can be a tough compromise. Also, what kind of what tones do you like? Are you more of the Dunlop kind of guy? Vox? Parachute? EMB? I think that one's wah tone should be very much a part of that person's signature sound. Not to blow smoke up my own ass, but I'm known for my live and studio wah sound. It may not be everyone's cup 'o tea, but it works really well for what I do, and it's different. But I digress, just a bit...
The Silver Machine was a cool wah. The instant on/off feature is nice, but I personally like the reassurance of a click. For me, I keep coming back to my trusty 535q live and in the studio, and my Vox 847 for strictly studio use. If I were going the pay the money for the Silver Machine, I'd spend the extra cash on a used Dunlop Rack Wah so I could get those long cable runs off the floor, and have the tweakability available. Of course, I'm very much a Crybaby kind of guy. If you end up liking the SM, then by all means go for it! I wouldn't say no to one, that's for sure!
Sorry for the rant, YMMV, IMHO of course.