I have used the extension tubes for a few months now, mostly with my 90mm (non LS) and 200mm f/4 (late) lenses. I was quite overwhelmed initially but now I get some really nice work with the setup. What I find most difficult is composition and framing and not having unwanted things coming in the picture and I don't pay attention to it in the waistlevel finder image. Focusing is no problems for me and proper depth of field is a matter of practise. Do you have the correction tables for lenses with the extension tubes? For close-up and macro I mostly shoot color negative - I apply the correction and then usually add about an extra stop or two of exposure to avoid getting black background areas. The lenses are both excellent and extremely sharp. The 90mm stops down to f/22 which may be a disadvantage whereas the 200mm goes to f/32. I hear some people recommending the 90-180mm zoom for macro. The minimum aperture is f/45. The lens is apparently very good but I have no idea about performance at f/45. I also have the reverse adapter which may produce some intriguing images but I have not yet tried it.