The 200mm f2.8L is my favourite lens of all. It's small, light and has outstanding image quality. It works very well indeed with the 1.4x, even wide open. It lacks IS which is a shame but other than that it is exceptional. I also have the 300mm f4 so I rarely need to use the 1.4x on my 200mm. However, the 200mm + 1.4x is smaller and more compact than the 300mm. I originally had the 70-200mm f2.8L IS but sold it in favour of the 200mm prime. The prime is far better in all aspects.