125k is a lot of miles on any car, most problems usually start to occur around 80 to 100k. You have to remember, the year and model you're looking at is a $70 to $80k sports car, so upkeep and repair costs will fit the bill. Problems will occur, just like with any car, but the bills will be more pricey given its an exotic car.
It's not an issue of bad design or engine problems, this is the BMW 6 we're talking about! Once you drive it and see that baby parked in the driveway you'll never look back, it's drool inspiring. Don't be afraid of the car, it's not even a car really, it's a finely engineered machine and a beastly one at that. Just purchase rationally and wisely, proper maintenance is key. If a CPO is out of your price range and you're worried about problems, an after market warranty might be a good idea, but they are pricey too and sometimes confusing as to what's covered.
The specific cars you're looking at are in the teens for a reason. Check the service history, how many owners, things like that. These cars are made to be driven. And some people drive harder than others, that will takes its toll. If you can find a 6er with one owner, they most likely babied it because they bought it new. If you find one with 3 or 4 owners, who knows what went on! Browsing the board, you'll see that there are some common problems with the 6er, others know more about them than me as I'm new to the game, but overall it's a solid car. I think it's an issue of no one posts when everything is running smoothly. My 2000 328ci had plenty of problems, most occurred in the 100k mile range as little things add up.
I'd say keep shopping around until you find one with lower miles, but you have to be willing to spend a little more. It will save you money in the long run. I got a great deal on an 05 with 43k miles, one owner and it's in mint condition, looks and runs brand new. I'm totally in love.
Last edited by GetMeABeer; 01-22-2013 at 08:50 AM.