Just posted this somewhere else, but thought I would put it here for future reference, in case anybody needs it:
It is possible to drive the E90 335i LCI MT transmission smoothly (dunno about the others, just referring to what I have)
You do not need a CDV delete or clutch stop or anything to drive it smooth, granted, getting the aforementioned might make things easier.
My number 1 tip for driving the 6MT we have in our cars smoothly is staying on the throttle when upshifting, i.e. revmatching while upshifting. Let me illustrate: say you're revving 2000 rpm in 1st and want to go to 2nd. Clutch in, but do NOT LIFT YOUR FOOT OFF THE ACCELERATOR COMPLETELY. Instead, go to like 1400 RPM, or whatever the correct engine speed is for your actual speed. Now, as you release the clutch, smoothly apply gas to keep the revs at the appropriate level. When the clutch is out, stomp on it, and then do the same for all proceeding shifts.
Like this, I can go from 1->2->3->4 at city speeds and you can't feel a thing, only smooth acceleration.
I don't even think about the RPMs now or look at the tach, I can just feel how much I have to move my foot. Learning the process becomes easier if you shift at like 3000 rpm or so, the engine has more inertia and you have longer to adjust your revs = easier to be smooth.
Other cars that I have driven (NA or turbodiesel) haven't required staying on the throttle as much as this car likes it.
ANY amount you stay on the gas (even like 0.00001mm depressed pedal) is better than having your foot off the gas while upshifting.
Of course, with your foot on the gas, you do not want the RPMs to climb while upshifting.
Downshifting, there is no need to move your foot off the accelerator at all, just revmatch.