I will chime in. I owned a 75 240D with a manual tranny. I got it with about 100,000 miles and sold it with 360,000. It still ran great when I sold it.
I never did much other than oil changes and 2 clutches. The main problem is rust. Trunk, firewall, floorboards, quarter panels etc. It was slow as hell, but I towed a small sailboat all over the country with it. The boat, trailer and gear weighed about 1000 pounds (snipe, lido 14, or a laser). It towed the boats just fine and got great gas mileage (~30MPG). The AC/defroster fans tend to go bad and are difficult/expensive to replace. Mine had manual windows/locks and a manual sunroof. I gather the electric windows tend to give people problems. The manual sunroof would slam shut when I braked hard (keep your hands out of the sunroof
). They are suprisingly fun cars to drive. Slow yes, but they handle well. The seat construction (springs) are better than the 123's, but the padding becomes dry, leaves piles of dust under the seats and gradually becomes uncomfortable. The suspension springs seam to last forever, but the various bushings need to be replaced every 15 years or so. My rear defogger quit working, I never looked into why.