Thanks for the pic Mack, it is nicely controlled but in these shots I do not see the punchiness of the 16-35 f/2.8L II sunburst (which has sharper/less diffuse rays). If Canon were to release a lens that could do rays as punchy as the 16-35 f/2.8L II, but as controlled as the 16-35 f/4L IS - now that would be awesome. I really love how commanding the sun looks in 16-35 f/2.8 II shots, however the uncontrolled nature of them (often extremely long) can be intrusive in pictures sometimes. I have to say for landscape in general, the 16-35 f/4L does look like the best bet for now! No problem and I haven't had enough time to get a good feel for the lens, but I think it will give some nice sunbursts with time & practice. Assuming the 24-70 f/2.8 II is pretty similar, I've been able to get some nice effects with it, particularly for cityscapes with night lighting.
The only other option might be the EF-M 11-22 IS, which has a similar design but with fewer aperture blades. That might be that sweet spot of dramatic, yet controlled sunburst. I've had one for a little over a week now, but haven't had a chance to test it out yet. I'll update you as I have time to shoot with it and the 16-35 f/4 IS of course.
Yes, the sunstar looks remarkably similar, if almost identical to the 24-70 II. Its not a bad sunstar, and probably less distracting than the 16-35 II's, but it isn't quite as punchy as the 16-35 II's (meaning the rays are wider and more diffuse, rather than thinner and sharper).
Does the # of blades affect the sharpness/diffuseness of the rays? I thought that it only affected the number of rays, and that to get sharp rays you need straight aperture blades instead of curved. However, everything I've read about the 16-35 f/2.8 II seems to indicate it also has curved aperture blades, so I am not sure about this one.