I made a difficult decision and sold my 400 f3.5 AIS to purchase a 300HSM. I will miss that 400, but I am looking forward to having the HSM on this lens. I have seen some outstanding work from this lens, so I am very confident of the IQ. I have a Sigma 1.4 EX already and it is a great tc on the 70-200; I'm expecting it to be even better on this new lens. Does anyone have any experience with the Sigma 2x? I'm wondering if that will be a worthwhile purchase. I used to have one for the 70-200, but I sold it because it wasn't critically sharp to my eye (not bad...just not great...the 1.4 is GREAT). My hope is that with the 300 2.8 being a prime, the 2x will be much better than it was on the zoom. I'm a wildlife/nature photographer shooting with a D200 and many film bodies BTW. Any first hand experience out there? Thanks all!