...... I want one, but the £17,000 (yes, seventeen thousand pounds!) price tag might put me off somewhat.
Sounds impressive specification though... f2.8 throughout the full 200-500mm zoom range, comes with a dedicated 2x converter that makes it a 400-1000mm f5.6 with autofocus working all the way. Sadly it has no Image Stabilizer and it weighs a hefty 15.7Kg. I also think the way it looks is more likely to get you arrested as a terrorist than a pap or bird watcher.
Take a look at this link to get the true scale of the lens.