Regret selling: Epson R-D1. A rare camera (less than 3000 exist of all variants) meant as a technical showpiece for the company rather than use, ingeniously cobbled together using Bessa film camera and Seiko watch parts, and a Nikon sensor! As an exercise is in industrial design on a budget, it's a tour de force, as a practical camera ... let's say it had quirks! If Epson ever make a 24MP version (never happening!), I'd buy it in a heartbeat! (I used to run the
unofficial R-D1 website, long ago donated to Cameraquest (unfortunately, the pages have technical problems so they don't display as they should - ask Stephen at Cameraquest to fix it: he has all the images and files, and the pages I originally provided worked as a stand-alone website).
Regret buying: Leica M8. A hideous, steaming pile of crap from a lying company! It was simply not fit for purpose. As well as the known flaws like having to use infrared filters, it turned out to be utterly unreliable and poorly designed, with problems such as failing shutters and sensors. Its software crashed if you took multiple shots, with the camera locking up and frozen - and like a dodgy PC, the fix was to reboot it by turning it off and then on, in this case by taking the battery out and putting it in again!
To add insult to injury, Leica took months fixing my broken shutter. Then lied to me: a major reason I bought the M8 was Leica's official policy that the camera would be upgradeable. New, better sensor? No problem, send us your M8 and for a fee we'll replace your old one. A few months after I bought the camera - after saving hard for it - Leica reneged on this promise. If Leica hadn't been so niche, it's possible that someone may have been able to sue them: we in Europe take a very dim view of companies pulling such stunts, and have extremely robust consumer protection laws. Leica left such a bad taste and treated its customers so poorly, that I'm boycotting the company for the rest of my life!