Update:
So as far as the steering rack itself everything bolts on
horaaaaaaaaaaaaay. Except for the tie rods from the M3 theyre a little longer. Now heres the trick just put the tie rods, either old ones from the d/i or buy new stock ones and attach them to the M3 Steering Rack. That is if you want to quickly get the car going and are not pushing them hard.
I suspect its because those who do not have M3 Control arms and suspension bits you will need to use original 335d/i or stock tie rods as they are shorter than the M3s. No biggie. So if you're planning to make your steering a little better you have two routes.
Rack first and use old arms, then upgrade them or Arms first then upgrade the rack. Unless you're a baller then go crazy and do both at the same time. Just remember to get an alignment haha.
I cant tell you how it feels yet as my car is still being worked on. Just wanted to confirm that the rack itself fits and any problems that you may run into.
Just for confirmation heres the DIY for the M3 Arms.
http://www.e90post.com/forums/showthread.php?t=788761
It adds a weeee bit of camber at the bottom and from what my bud said the M3 rods are a weeee bit longer bout an inch or less. I know you can adjust the rods closer but the plan is to replace the rods anyways so ill bunch it up with the M3 Arms when the time comes. Meyle HDs are nice