Just as a point of reference on other BMW's, as I said buried in my first post, the 335d has occasional turbo lag, but very minor tip-in delay. Another way of saying that is throttle response (aside from the turbo lag) is linear and predictable, if not outstanding.
The X3 35i has a specific problem related to tip-in. It was worse before the software update, but still happens. This is felt as an inability to predict how the car will respond when you press the accelerator from rest. It is especially noticeable when traveling on a street with a number of stop signs. It is improved in S mode but still not eliminated.
So: in the 335d, I know how the car will respond to my throttle inputs; in the X3, from rest, I do not. If the X1 is also like that (I suspect it is), it's very discouraging.
dd: 2014 X1 xDrive 28i MSport
in garage: 2011 Mazda MX5 Miata 6mt
Wife's car: 2012 X3 35i
2008 328i 6mt
2005 325i 5mt