When using an iPhone 3GS headset with remote and mic with a Nokia E7 I observed it doesn't seem to be working properly. The mic was too weak and the sound heard in the headphones was distorted.
Tip: Holding down the headset's microphone/answer button makes the Apple headset behave like it should on the Nokia E7 (may work with other models too).
Warning: This is just something I found out when toying with the Apple headset. (use this with caution as it may have side-effects...)