Residuals are important because on a new car depreciation is by far the highest cost of ownership for the average miler, dwarfing fuel cost differences. I don't think of buying a car like buying a TV. I feel like i'm borrowing it for 3 years and ask myself how much it will cost to borrow it, because no one keeps a car for 12 years these days to run it into the ground.
I wouldn't consider a car I wouldn't be happy driving, just because it has excellent residuals, but it is a consideration I would put a lot of thought into when considering my shortlist. Better cars usually have better residuals so you're not in the position where you would put yourself into a crap car because it holds its value well.
I think about absolutely everything when i'm going to spend £26k on a car. The car itself - how does it drive/look? How well equipped is it at standard spec? Whta extras would I consider essential and how much are they going to cost me? Is the insurance going to be daft? Will it cause me to wince at the pumps due to it's thirst for fuel? For me the GTD was the best overall package, cheap to run comparative to it's RRP, drives well, very well equipped as standard (I felt no need to tick the options box). Couldn't want much more than that out of a car. A3 was up there for similar reasons but fell short on standard equipment, no availability of the 184TDI engine at time of ordering the GTD and slightly superior interior quality/look (S-line) in the A3 didn't tip the balance in it's favour.
Runflat tyres are my biggest bugbear on BMWs. They spend so much time and effort trying to get 50:50 weight distribution etc for their handling and then go and put Fred Flintstone tyres on and ruin ride comfort - why do they do that? No-one likes them, they ride horribly and are disproportionately expensive. If you must do away with the spare then surely self sealers are the way to go.