I think they're ok actually. Decent power in a little car, and the chassis of the later ones was much improved.
People generally prefer the RS Turbo, simply because it has a turbo, but that was hardly a gem either, with wild torque steer and a worse chassis than the RS1800.
Sadly there's a lot of snobbery and put downs amongst Ford enthusiasts, but fuck 'em, if you like them, buy one. I'd rather pay £12-1500 for a nice RS1800 than £2k for a rotten to shit RS Turbo.