There are a lot of ways to tackle the shift feel in our cars. The cheapest and easiest would be a shift knob change. It is amazing how much of a difference a shift knob makes on our cars. (Shameless plug for my MANY reviews of shift knobs thread
https://www.zpost.com/forums/showthread.php?t=1492392)
CDV mod or delete and fluid change (Royal Purple Sychromax for me) would be next. I too noticed a difference with these changes. Both are fairly easy for a humble DIY'er to do, and a shop shouldn't charge too much for either service.
Next would be both engine and transmission mounts. Limiting the slop with better mounts improves shift feel even more, however with a minor trade off in NVH. I went with the VibraTechnics Road mounts and Rogue Engineering transmisison mounts. Small NVH increase, however definitely tolerable most of the time. I will note that if you live anywhere that gets under 30 degrees Fahrenheit and you drive your M, the VT mounts make the car shake a bit and be loud until they warm up from engine heat. This is a more involved DIY and unless you are mechanically inclined, have a shop do it.
Finally, new shifter assembly. I went with the Autosolutions SSK and it is VERY different. Eliminates nearly all of the slop, and feels almost like a gated shifter. I will note your shift knob choice will make a HUGE difference here, depending on your shift feel preference. Again, this involves some more advanced DIY skills (dropping exhaust, drive shaft, etc) and if you are not so inclined, have a shop do it. If you are considering a DSSR, do it at the same time otherwise you will be doing this job again!
At the end of the day, I have found the above mods with the Jaffster delrin shift knob from bimmerworld is just amazing. The best shift feel I have felt in my car by a long ways. No notch, period. However, since the Jaffster kinda looks like a simulated phallus, I run the weighted OEM style knob for daily use, which provides about 80-85% of the shift feel provided by the Jaffster, with minimal notchiness.
Caveat here. Even after all of these mods I still occasionally 1-2 grind at an autocross. It has lessened the occurrences for sure, but it still does happen. At the end of the day, all the modifications in the world will not fix a driver who has an impatient left foot!
