Very nice lens, great photos, a little heavy

To save you looking up a more detailed overview of this lens I have included it here:

The Canon EF 70-300mm f/4-5.6 IS USM telephoto zoom lens has been developed to meet the high-performance standards that today's photographers demand. The telephoto effect can make the picture look compressed or have excellent background blur. At the 300mm focal length, you can fill the frame with a postcard from 4.9' away. Ideal for sports, portraiture, animals, etc.

Improved Image Stabilizer Technology provides up to three stops of "shake" correction, and the "Mode 2" option stabilizes images while panning with a moving subject. Compared to the original Canon EF 75-300mm IS zoom lens, this telephoto lens has faster autofocus, and overall the lens is lighter and has a smaller diameter than the original.

Key Features

• IS Image Stabilizer
Image Stabilizer allows photographers to use shutter speeds up to 3-stops slower with no perceptible increase in image blur. For stabilized panning, IS Mode 2 only corrects for unwanted vertical shake by switching off IS in the horizontal direction. IS is ideal for low light conditions, fast paced scenes and for shooting from moving vehicles. IS switches off automatically when the camera is mounted on a tripod.

• Micro USM Motor
The Micro USM motor uses ultra-sonic frequency vibrations to drive rapid auto-focus with near-silent operation. Good holding torque ensures there is no overshoot. A high speed CPU and optimised AF algorithm contribute to AF speed literally faster than the human eye.

• UD Lens Element
A UD (ultra-low dispersion) glass lens element corrects chromatic aberration to achieve high resolution and contrast throughout the zoom range without colour fringing on subject outlines. Only lead free glass is used in the lens construction.

• Super Spectra Coatings
Optimised Super Spectra lens coatings and lens element shaping suppress flare and ghosting, more prone to occur with digital cameras due to reflection off the image sensor. Coatings also help achieve true colour balance and sharp high contrast images.

• Pleasing Background Blur
Circular aperture (8 blades) provides pleasing background blur.

• Secure Transport
The zoom ring can be locked at the 70mm position, making this lens easy and more secure to transport.

Overview
Now that you know the details about it, how does it perform? We I've taken quite a few nice shots with it, and I am very impressed with the images I've taken. The image stabilization works great. I tested it with the IS on and off, and it really makes a huge difference. The zoom and focus works really smoothly, and it syncs nicely with my Canon 400EX flash (the 400EX receives the focal length from the lens and automatically zooms the flash up to its maximum zoom of 110mm). The only complaint about it came from my wife when she tried to pick up my camera with the lens and flash attached and she exclaimed..."My god this thing is HEAVY!"

Image Stabilization
The lens has 2 modes for image stabilization and I tend to only use mode 1 which it full IS- meaning it stabilizes both vertical and horizontal shake. Mode 2 only handle vertical so that if you are, for example, tracking a speeding car, it doesn't try and stabilize the background behind the car, but only the object not moving vertically (the car). I tested this and it works great, but except for the odd eagle, I'll probably not use that option often.

As for the other features listed above, the only other one worth mentioning is the lock switch that allows you to lock the zoom ring during transport.

The most important thing about a lens is how smooth it is, and most important, how clear and clean are the images. This lens produces great images!

It is a little on the expensive side, and as such, it had better take good shots! Camera's with built in IS make a lot more sense as you wouldn't have to have it incorporated into every lens, but I'm not sure if that approach would work as well.

Overall I couldn't be happier with this lens.

PAID $568 on Amazon. Originally ordered it from Profeelvideo.com, but they called and tried to sell all sorts of extras which I declined, then 2 weeks later said they were still waiting to get it in stock (when they said they had it when I first ordered--perhaps I need to review them next!)