I have owned a bike with full SSC groupe for over 25 years ("gruppo" is an Italian word and IMHO should only be used for Italian components, "groupe" should be used for French components and "groupset" for others ;-) )
The Mavic SSC components are indeed a mixed of outsourced components.
The erector set rear derailleur works very well on very tight corncob freewheels if you move the cage all the way to the top of its adjustibility, but is hurt by the Simplex retrofriction levers that require much more movement than most other levers with bigger barrels. If you go to wider range freewheels it works better than Campagnolo. The loose derailleur stop clip is a stupid design as they invariably get lost when you remove the derailleur from a bike. It should have been attached to the derailleur in one way or another. Most people are also not aware of the fact that you can adjust the height of teh cage to suit your particular freewheel. It is more durable than most Japanese and other French derailleurs, but not quite as good as most Campagnolo derailleurs. Overall judgment: OK!
The front derailleur is no better or worse than any number of other derailleurs on the market. Overall judgment: OK!
The original SSC brakes were simply rebranded Modolo Master Pros and were every bit as good as anything else available at the time in the early 80's. I prefer them to Campagnolo because of the better lever hoods, but it is a subjective matter at best. By the late 80's, there were many far better brakes available. Overall judgment: OK to better than OK!
The headsets were among the best around, but required special tools that are hard to come by. They also require very precise machining of the frame and fork (much like King headsets). Once they are installed correctly, it is pretty hard to damage them. If you have access to the tools: Overall judgment: Exceedingly good! If you don't have the tools fuggedaboddit!
The BB's were equally among the very best available, however did require special tools for installation and once you had installed a Mavic BB, it was at times difficult to use anything else. I'm not sure of how easy or difficult it is to get replacement bearings for the BB. This is however definitely not a wear item and is very robust and long-living. If you have access to the tools and plan to leave the BB in forever: Overall judgment: Exceedingly good! If you don't have the tools fuggedaboddit!
The SSC hubs are also among the longest living components around, both as regards bearings and finish, but the skewers are not up to the same quality standard. I would take most other skewers over Mavic skewers. The non SSC hubs had the freewheel side bearings inboard of an adjustable cup that made it last a bit less than the SSC model that had the bearings outboard. Overall judgment on hubs: OK to better than OK! Overall judgment on skewers: fuggedaboddit!
The original SSC cranks are nothing special, but did use 144 BCD, so to find replacement rings is very simple. There is nothing wrong with the cranks, but I wouldn't go out of my way to buy them unless the price was interesting. I offered a clean set for sale at the recent Trexlertown swap for $60 a pair (less than the value of the chainrings!!) with no takers. The starfish cranks came subsequently and I too agree that they were ugly. Overall judgment: OK!
The original SSC quill pedals are also extremely long living and on a par with TA pedals in my eyes. There were surface oxidation problems with the chromed bits but that was minor. They are also slightly larger than Campagnolo and clones. The hard anodization also lasts considerably longer than the black anodization on Campagnolo and clones. The subsequent Look-produced clipless pedals are acceptable but nothing special and wear out like all Look pedals. Overall judgment: OK to better than OK!
The Mavic handlebars are a matter of personal preference. They are reasonably rigid and enough differetn patterns were available so that you could likely find something that makes you happy. Overall judgment: OK!
The Mavic stems were a bit more flexible than those of many other manufacturers. Overall judgment: OK!
Overall, nothing bad bad. It is more a groupe that suits itself to those who want to be contrary and anti-conformist; however, if you can get yourself a deal on the whole groupe it is definitely worth it, especially if you have access to all the proper tools.