Based on
almost no existing poor reviews about the net, I ordered this lens to fill my need for something past 70mm in my kit. This baby "L" tele is extraordinary. The color saturation and contrast are beautiful, without much need (ever) for post processing in these regards. Sharpness is fantastic across all corners of the field, and that's wide open at 200mm (which is where it spends 80% of it's time). I see zero CA in this lens.
Mechanically the lens is solid and tight, while having very smooth ring action for both the focus and zoom. Auto focusing is very quick, and amazingly quiet.
I marked "none" for negative aspects of this lens. Although it does have the following short comings: it's not 2.8, it's not waterproof, and it doesn't have IS, for the current price (less than $600 USD) how can you complain.
It's my current favorite lens. The image quality is so good that I'll even use it in tight situations where a shorter FL lens might be more appropriate, instead using my feet to frame.
As a birding lens? Well, it's 200mm (320mm with an APSC). Not exactly what you call
long. Still, if you can get close, you can do very well. Even cropping down retains some excellent detail.
If you are shopping in this FL, and have a moderate budget, buy this lens with zero concern.
Samples:
http://farm3.static.flickr.com/2413/2398886752_1d754bbc5e_o.jpg
http://farm4.static.flickr.com/3225/2403512977_5a8d813e6f_o.jpg
http://farm3.static.flickr.com/2246/2512376822_22882cc146_b.jpg