These are fantastic machines, if you take the time to get them at least back to original condition or preferably better. A lot of the common complaints (e.g. poor front brakes) are easily and fairly cheaply fixed.
I bought my bike, a 1980 CX500C, in very poor condition for $300. I totally overhauled the bike, and now it is just amazing. The tuned-up engine and replacement ignition accelerate the thing quickly and smoothly to 65-70 mph, where it will happily and steadily cruise all day, even in the hottest weather. The front disc brake with single-piston caliper hauls the 460-lb motorcycle back to a stop surprisingly quickly - the stainless brake lines and new master cylinder make a huge difference.
It starts instantly in any temperature and never bogs down. You can ride right off from cold starting (unusual in bikes from this era and even today)
Handling is pretty excellent. I have new shocks and rebuilt forks, and the forks are lowered 1" in the trees, which quickens the steering just enough. The center of gravity is fairly high, but it doesn't matter once you're moving. The tires (new Kenda K671s) are excellent in all conditions, with tons of grip.
The seat is comfortable, the bike looks nice (with the addition of a new paint job), and sounds nice because of the new mufflers.
Total cost for the build was roughly $1000. It took a few months, during most of which the bike was rideable. No work was outsourced - I did everything myself.
Full list of modifications:
Front brake caliper rebuilt. New pads and fluid. Replacement (improved) master cylinder. Stainless steel lines.
New mufflers (stock Harley Dynas). These are reasonably quiet and very deep. Excellent sound.
Ignitech replacement ignition module. This replaces the aging CDI unit on pre-1982 bikes, and solves problems with that and the stator (both chronic problems with the CX). It also has an improved curve programmed, which improves performance, ease of starting, and smoothness over stock.
Thoroughly cleaned carburetors, properly synchronized.
Rebuilt front forks, lowered 1" in the trees.
New rear shocks.
New engine water pump seal (also a chronic problem).
New fluids all round.
Cleaned and lubricated cables.
Restored seat (original foam and repaired original cover).
New ultrabright LED signals and stop/tail light.