I've had several autos, no problems, and I'd be more reassured that an auto was going to carry on working if I could see the service schedule had been kept to, than a manual (given that a manual trans life expectancy is very much down to the human driver element: you just can't know how much that clutch has been slipped/gears ground etc.. autos are computer controlled and can't really suffer these things)
My dad always looked for evidence of a lazy driver, or even asked the owner (if they'd had the car a long time) to do the test driving, so he could assess how much they abused the machine.. clutch pedal rubber worn away on one side, scratches around the door lock (unusually indicates "one careless lady owner" though in this day and age of remote locking, less of a telltale) etc
The one thing that buying a high miler may preclude is purchasing an aftermarket warranty.. I've never been interested, chiefly because when I was young, I'd buy a 500 quid car and throw it away after a year (and now i'm old, I buy a 5 grand car and throw it away after 10) so warranty didn't seem to make much sense. By similar measure, I don't think I can get twice the car for ten grand than 5 grand will buy you.. example the Vauxhall Insignia mentioned before.. Should be able to get a 3 year old 70k one for five k (all values approximate), and it'll be really good value at that. The equivalent Audi might be 10k, but it's unlikely to be twice the car. Depends on how badge oriented you have to be..*
Said the man who wants an E61 M5 as his next shopping trolley/baby bus (but will probably still be chugging a Volvo round while m5s go out of fashion, then buy a 6 series, because they're much better value, performance wise)
*An excellent point you made earlier (possibly without realising) - by going for a lesser badge (even from the same stable eg Seat/Skoda vs Audi/VW) you get more kit on the same chassis for your money.. A £10k 3 year old Audi A6 is more likely to be the base model than a £10k 3y.o. Superb, Insignia, Mondeo etc.. Would I forego an Audi badge to get heated/cooled leather seats with electric memory (so I don't crack my knees every time the wife has been driving), cruise and the upgraded audio? Damn right..