I have been compelled to upgrade to a great birding/wildlife lens but cost, size and weight of most high end lenses are factors to overcome. This has to be the best available option in the Canon fixed lens lineup. Have really been impressed in the few weeks of use. Sharp, quick and really can be hand held for decent shots but will prop up or use support/tripod when available. Love the image stabilization. Also added the Canon 1.4 extender and flash and can't wait for upcoming opportunities.
