The getrag transmissions have always been a bit notchy and my E90M3 is no exception. I picked up an '08 with 19k miles, it is notchy. The 1->2 shift is smooth, but I think most complain about the inability to shift fast from 1->2 and this may be because the ratios are spread out much farther from 1st to 2nd. The other gears are more closely matches so maybe their synchronizers are designed differently for that purpose of use, especially on a track where 1st may not be used nearly as much as 2->5? Just guessing here.
08 E90M3 6MT Alpinweiss/Schwartz/BMW Pedals/Dinan Exhaust/ZHP knob