We purchased the 525i to replace a Q45t Infiniti. It is a different world. The BMW is much more sporty than the old pillow barge but it is not as comfortable on long road trips (we drive it to Seattle almost every year, ~ 3000 miles RT). I find the drivers seat small and cramped, although my wife likes it fine. Handling is good and the ride is adequate. The 4 year $0 maintenance is good and it was needed. A lot of small problems including a bad window motor, broken cup holders, dashboard computer replaced.
Spectacular gas mileage. Holding at 65 will give 38 mpg on the highway. Averaged 32 mpg over a 1000 mile trip. Solid handling on the road. Great trunk space.
The iDrive is awful, a product designed by engineers for engineers. Cup holders are flimsy and poorly placed. The center console is unusable.