The future Safari Lens?

For years we've been struggling to recommend the perfect lens for our photo safari participants. Nikon's 80-400 is sharp but slow and old and Canon's 100-400 is unpopular due to its push-pull operation and many samples are quite soft at the long end. It's not a speed daemon either. But after handling a Sigma 120-400 at PMA I'm hoping we've found an alternative that will work for everyone. I'm getting one next week and will be shooting with it and letting participants shoot with it in Texas & Alaska so I'll be able to report back with a full field-test.