Re question of chipping, or not: By all means, go ahead. There is no real downside, other than the cost. But the better bang for the buck is the installation of motorsport cam gears. This is not a cheap conversion, but the increased torque makes the everyday driveability of the car well worth it.

The consensus on the cam gear is that Dinan charges way too much (original BMW part that can be bought for somewhere around $100) and if you know the part and can get it installed cheap, it is barely worth it. I got the D'Sylva chip and am quite happy with my lowend grunt.