I'll be the first to say I just did this.. I had the new pre on the charger, sitting next to him was my old 755p (which for some reason still works with vision / web..odd)

I needed to run out to get some things so as I'm walking out I went to check the pockets to make sure I had everything.. just to realize I grabbed the wrong phone.. lets just say the old phone is now tucked away inside his coffin (the pre box) so that won't happen again.