I don't think DS effects steering, it's only for the transmission (on my car anyway).

Can't wait to try it out on my car.

Umm.. if you are checking your Safety Gateway Module and it does have FDC in there I'm pretty sure that if you engage or disengage it the option would change. However I don't know if the FDC is the same FDC discussed here and I don't know if it's stored in SGM ZGM

I'm sure it will.
I'm certain it's the same the same FDC 'fahr dynamic control' discussed here, here's a quote taken from the BMW TIS document:
"The SGM before 09/2005 or the KGM from 09/2005 switches the "Servotronic" or "Active steering" option to a more sports-oriented characteristic. Steering and holding forces on the steering wheel are given more sporty settings."

...the tighter steering seems to be the main thing people notice after doing this mod anyway so I guess the fact that there is a reference in the SGM/KGM is irrelevant to us if it's already working without coding. I just thought it might have been worth a mention for people that don't seem to notice much of a difference after the mod.

I read somewhere that servotronic wasn't standard on E60's until the 09/2005 builds (it was an option prior to that). May explain why I don't see any steering changes in sport mode, only throttle/shift changes. Anyone else with an 04 or early 05 model notice this?

I haven't added the sport button yet, but I don't think I have servotronic either (my build date is OCT 2004) so perhaps I also won't notice any steering changes. Although I would say my steering is quite tight/heavy anyway. I had driven a LCI E61 some time before buying my E60 and I can't say I remember the steering being as heavy as mine.

Do you notice much of a difference with the throttle? (this would be my main reason for adding the button)

By servotronics, do you mean active steering? If so, I have that on my 04 545i as well as Dynamic handling.

I believe servotronic and active steering are different things. According to my car's VIN, I have servotronic, however I don't have active steering.

I have AS and DD and I have noticed that in D/S the EGS/DME are changed a bit due to RPM difference but not much.
The FDC "sport" button doesn't do sqat. I have tested in all type of driving even up to 135 MPH as you can clearly see from my pics and it doesn't changed the steering feel to something noticeable. Sorry
As far as those talking about not getting a 6th gear in D/S mode, with this tranny you're probably mistaken. It is in 2nd gear the entire time so if you are counting then you are on 6th. At least that's how it is for me and I would assume others that have a sports edition E60.
So do the mod if you want but do not expect a miracle.

I do feel a difference in that there is less initial 'lag' or delay in the very early part of the throttle travel, but no change after that like what a sprint booster is supposed to do. Also don't notice a change in the shift points compared to DS, but I do feel it is more willing to downshift and tends to hold the gear longer on upshifts.

i have 04/04 no servotronics but I do have active steering no change on steering with the sport enabled but the throttle response changes!