I bought a set of 600SE to set up a photobooth, complete with 2 studio strobes, at a colleague's wedding reception. The reaction to these FP100c prints, especially compared to the digital prints, was overwhelming positive.
The 600SE is a wonderful camera, and if you have a chance to get the complete package with all 3 lens, you should go for it. Or introduce me to your friend about the deal if you decide to pass
The 127mm lens carries the usual Mamiya signature: razor sharp with beautiful color rendition. The biggest problem that I find with the set up is its bulk, which made it almost impossible to fit into most camera bags. Not to mention that its hard to hide it from my wife at home. Mine came without both the body and the rear lens cap, so dismantling the set for transport wasn't an option. The camera has a second weak point: the shutter release cable is prone to getting cringed, if it is not disconnected from the lens when you set the monster on the table. When the cable gets cringed, the shutter release becomes less smooth.
Overall, I really like the camera for taking instant shots. I'm not too hot about using it also as a film camera, for which there are many (slightly) more portable options, such as the Fuji GW690. I like it also for the fact that it is usually priced lower than the 180, 185, 190 and the 195 series of Polaroid cameras. In your case, if everything is available as a single package, then you should get them all.