The “Bigma” is probably the widest range telephoto zoom available in a high quality lens. A favorite among nature shooters and “everything” shooters for its great range and good image quality. Nothing else does quite what this lens does.
There are trade-offs, of course. This is a large lens, consequently, most photographers need a tripod for really sharp images unless the light is excellent. For those who want to shoot handheld, the Olympus 70-300mm may be a better choice.