In my opinion the extension tubes MCEX-11 & MCEX-16 are not a must if you already have a macro lens, but are useful if you’d like to use your other lenses for macro. The three pictures below are handheld, using both tubes at once, and only cropped to square.
60mm macro with MCEX-16. You can get closer, but for me the MCEX-11 is easier:
Added 2.9.2015: X-T10, 50-230mm OIS II, MCEX-16 or both tubes.
Big advantage: you don’t have to get so close to the subject:
Lego as an international measuring unit? :-)
X-T1, 55-200mm, at 200mm, left without tubes, right with MCEX-11 and MCEX-16:
18-55mm, at 55mm, left without extension tubes, right with MCEX-11 and MCEX-16:
60mm macro, top left without extension tubes, top right with MCEX-11,
bottom left with MCEX-16, bottom right with both tubes:
Earlier examples with the 60mm macro and the extension tubes, February 2015.
Comparing the 60mm to the 80mm macro, January 2018.
For comparison: the X100s with no converter / TCL-X100 / WCL-X100.
I’d have expected the TCL-X100 to get closer than the WCL-X100.