I use it mostly for portraits and photographs show.
Shows: it is not too bulky (despite the rather long sun visor), its maximum aperture is valuable (I use most often open between f / 2 and f / 4), and the interesting focal length. In this situation, the lack of stabilization is not a problem since usually the subject is moving and therefore MUST anyway shorten the exposure time for a generally low light. The development is rapid, it is essential for this use. Obviously the focus needs to be precise, because the depth of field is limited to these openings.
The benefits under the opening, which helps fast framing (with a fixed focus, we are still forced ...).
Shadows of lighting and materials from projectors on stage are particularly well restored.
For the portrait, 135mm, faces are well rendered (no effect "crushing" significant, as is the case with telephoto lenses of 200mm or more), and we can still stay away, thus favoring spontaneity. On portraits in tight framing, I find the perfect formula with a 24x36. It can be opened to the max, the loss of sharpness (for the purists) on the banks is irrelevant for this type of shooting, and f / 2, the depth of field is very short to 135mm.
On an APS-C, it pulls like a 200 f / 2, which also makes it very attractive for its price and weight, those who tried the 200f / 2 Canon should include (but with an APS-C stabilization is running a little ...).
It is compatible with the converters (x1.4 and x2). With the x1.4 (III), I find the sharpness even when losing a lot, and I imagine (not tested for my case), it's worse with the x2.
Attention Front lighting, contrast is very impacted. What bothers here is not the appearance of ghosts spots, but a halo, and iridescence. Those who pose a filter before (like me) have to be removed in this case for further avoid degrading a little more, unless a specific rendering wish (say "cottony").