C-5 thru C-9's are solid saws. They have older style points ignitions and carbs but can be setup (tuned up) to be really easy starting saws. I think part because of the heavy fly wheel/crank (longer stroke than newer saw means larger crank halves) and part because the low rpm characteristics of the ignition just simply make it easy to get them started. (I also suspect the longer stroke means there probably is more volume change in the crankcase than a short stroke saw helping make a strong pressure pulse for the carb diaphragm at start RPM's) I happen to like running my C-7 and It happens to have the internal clutch (external ring sprocket) making cleaning and changing bars easy. They are an over designed saw that if in reasonable condition will out last you...they cut well with a .404 chain. I have blended Stihl bars to mine. If its cheap grab it and run it saving your more desirable collector saws.... The bigger XP1020 & 1050 don't have much more RPM's & therefore chain speed so for wood under 20 inches aren't that much faster. My C-7 wears a 20inch Stihl bar w/ .404 chain where my XP1020 has a 32 inch roller tip bar & .404 chain. They get used from time to time..hard when my favorit Homie's, the XL-925's & 903's are in the truck. But if you like the C-style & XP Style saws, a C-7 is a great addition. More useful for most things than the harder to start & more violent XP1020-1050's. (Just harder to pull over!)
I guess another way to look at C-7's, is they are actually a practical saw to use even now. They are easy to start, cut reasonably well, easy to work on, and are easy to clean & maintain day to day. Where as many of the older saws have collector status, the C-7's really don't, but in fact are as or more useful than the bigger saws of that style...so what will happen s the bigger ones get the decals and paint jobs while the C-7 will ...work and make short ones out of long ones, all day long. Year in year out. Down side? Weight & chain speed.
Starter issues? Mine has a blue C-5 arraignment. It works every time. The thing is with those C-Series there is a lot of mix and blend possibilities with other C-sereis saws. Makes that series more fun than some because they are frankensaw capable and cheap to find parts saws. They are a good choice of series to collect & mess around with for a guy who likes the tinkering as much as the cutting.
