My two cents.
Per the manual: BMW does NOT recommend tire rotation. On my M3 this isn't possible because the rear rims are wider than the fronts and all four are directional tread... So I couldn't if I wanted too.
That said, my BMW mechanic (something like 35 years of working on BMWs) once told me that BMW's off-line comments regarding rotation goes something like this. "Tire rotation is a procedure used to offset the effects a poorly designed automobile has on tires". . Considering how the tires wear on my M3. . Must be some truth to that statement because all four wear out consistantly and at the same time. The rears are worn a little harder, but both fronts and rears require new tread at the same time.
In any case... Lotta old timers talk about the curse of switching direction on a radial tire. Conversation with numerous tire reps indicate that this is an "OLD" issue which used to plague radials. Appearantly this has been resolved and is no longer an issue. Guess this could be argued to death. . but I will say this. I rotate front/rear and side to side. . as is recommended in the owners manual of the vehicle in question and I have never had an issue in doing so. Granted, I probably only have about 500K miles on tires rotated in this manner. . but I'd like to believe I would have seem a problem in that time if it was an issue. Hey listen. . if I knew all the answers. . I'd be rich enough to have someone drive me around in one of my many trucks. :-laf