I just wanted to post my experiences with this as I just replaced the shocks/struts and mounts on my E46 this past Sunday. Mind you this car had 153k miles on a completely original suspension so it's mostly just with age. I had symptoms of the whole car having a "shifty" feeling when going over expansion joints, the rear end was sloppy and liked to kick out a little when going around corners at higher rates of speed, and on rough roads you could actually hear the struts rattling in the passenger floorboard.
Got the rear shocks out first because they were easiest to do and they were completely dead. As in there was absolutely no re-bound when you pushed it down into the shock. I was basically riding on springs back there, and that explains why the rear end was always so finicky feeling. The mounts didn't look bad and had no cracks but I replaced those and put the new shocks in. Moving to the front was more difficult and since this was my first suspension install I was very careful. The front struts didn't appear to be as bad with rebound as the rear shocks, but they were still used for sure. The strut mounts though, they were bad. Looking underneath the mount the whole area was cracked around the mount. On top of that, the rebounds were so harsh from the struts that both front bump stops were destroyed.
Got the springs mounted on the new struts and had the car aligned and the difference is insane. The car handles so much better now. The ride is smoother and much more responsive when going over bumps in the road. There aren't any funny noises coming from the car any longer. It tracks better down the road, though I still need to replace my RTAB and such and get an alignment at BMW because the car pulls to the right a little bit. I didn't pay for that alignment so no biggie there. My whole point here is if your car has any symptoms like my car did and you have over 100k on an original suspension, do yourself a favor and go ahead and get it replaced.