I would really like to get the zuiko 21/2 for it's close up performance (floating element design) myself but don't really have the cash for it. Currently I'm using the 21/3.5 instead, mostly for close up portraits!
Those lenses can focus down to .2m, where the subject isolation is great, even with smaller apertures!
I also have a cv 21 for the Leica, but it's hard to focus since it only couples with RF to .7m, which is often a bit far off with a 21.
It requires some thinking to use since it's difficult to exclude things from the shot, but if you can get close enough it's very rewarding.
It's great to use in the dark with flash,since you won't need to focus very accurately at f16!
It's also very good for self portraits, where you can make use of the DOF and wide angle to capture the interesting environment you're in.
Truly a focal length with infinite possibilities!
I'm sure that you can do just as much with the 28mm, but people saying that the 21 cannot be used for this and cannot be used for that are just uneducated. Except for the fast 50mm, 21 is my favorite and they see a lot of use on my cameras
🙂