On a slightly different tack, I was wondering what the old lens is like? I need a zoom of this range for animals and sport moving toward and away and I've missed a few shots with the 300 prime. The prices seem ok, used top quality ones are a decent price. Best buy one before the price changes. New one will be a bit sharper, better I.s and lighter but way more expensive and for what I need the old one seems good enough. So is it any good? If not any alternative zoom? It's the wide range and a zoom I need.
I suggest you rent one first.
I bought one and returned it two days later. Not because of IQ or focus speed. Optically, I liked the lens and the images it produced. I just could not get used to the push/pull zoom.
I shoot production photos for theaters in my area. Generally these shoots take place during the final dress rehearsal when they run the entire show without stopping as if an audience is present. I get the run of the empty house...can go anywhere I need to within the seating area. I have the 70-200II on my 1DX and the 24-70II on my 1DIV...using the 70-200II for 85%+ of the shots.
On two recent occasions I've been asked to shoot the same show again to get shots of new cast members. The most recent was because the male lead in "Singin' in the Rain" ruptured his ACL during previews and they had to bring in a new lead. The media hadn't reviewed the show yet, so the producers wanted the newspaper & web review sites to have shots of the new guy.
They never did another dress rehearsal, so I had to shoot during a show from behind the audience...behind the back row. I needed more reach and the 70-200 wasn't enough.
I'd shot like this before using the 1.4 converter on the 70-200 and that setup was ok, but I decided I had to have the 100-400. You wouldn't think it, but shooting a musical with a lot of movement and dancing is a lot like shooting sports, except the lighting is constantly changing.
The push/pull zoom of the 100-400 slowed me down. When zooming in, you are literally pulling your camera away from you and when zooming out you are pushing your camera into your face. Plus, I had to change the way I hold my camera. I usually zoom using a finger on my left hand while cradling the lens in my palm...this wasn't possible with the 100-400. I shoot in manual mode and I'm constantly changing aperture and shutter speed along with continually moving my focus point around the viewfinder. This technique is second nature to me, but the push/pull zoom was very distracting and I know I missed shots that I wouldn't have missed. I just wasn't as fast with that lens.
In the end, I wasn't willing to change the way I shoot to accommodate one lens. I hope version II of the 100-400 will have the traditional zoom. I would buy it in a heartbeat.