I've looked at BMW Minis, and continue to be as impressed with those cars as I am with Miatas. Getting it correct out of the chute, like with the Miata, is quite a feat.
The caveats of these cars, however, are time and $$$. Engineering-wise, now is the time to buy a Mini. Soon, the next generation Mini will come out, and from a couple of the BMW Minis boards I've seen, the new ones will be heavier, longer and lack the rear suspension the current Mini has, which, in part, enable the car to handle as well as it does. This decision, in part, came as a cost issue for BMW.
$$$-wise, I don't know what sort of deal you expect with a used Mini, as Kelly Blue Book rates the standard, S and JWC versions as having very little depreciation. Some used models are selling close to their retail off-the-lot price three years
after being purchased.
Given that, wouldn't it be funny that in, say, five years' time, you're able to purchase a used Lotus Elise for around the same price as you'd pay for a used BMW Mini?
Or how about this: for the same money spent on a used standard BMW Mini, you could almost buy a vintage Mini Cooper S with a 1275 engine. Sure, they're smaller, lack at least one additional forward gear, and if you're hit by anything larger than a Moped, you're in for a visit to the hospital, but I bet the old Mini will run circles around its 2600-pound descendent in a canyon or on a track.