What can't the Olympus OM-D Em5 do as well as a DSLR/SLT camera?

I agree with you to a point.

However, whether one has used the EM-5 for a long time, or no time at all, it is as clear as daylight that the ergonomics are extremely poor but .................... brilliant given the decision to make the body as small as it is and to then cram a massive (relatively speaking) LCD on the thing. I have small hands, and I find the EM-5 ergonomics quite uncomfortable unless the accessory grip is attached (as the shutter button is positioned further forward in a much more natural position for the hand/forefinger with the grip attached).

As to your point about our bodies adapting, that in reality is a bad thing (ask any physiotherapist or chiropractor). To give an example, my current car is much more comfortable than my last; my body had to some extent accommodated the bad seating of the previous car (i.e the feeling of discomfort and pain had somewhat subsided) but it wasn't until I got this current car that I realized how much tension my body was under. In other words, lurking beneath the surface were serious posture issues hidden by, to use your words, my "body adapting to new ways of doing things".

When I move from a small mFT cam to a bigger cam I often immediately feel the relief, which tells me that whilst I may not notice it, there is some tension there when I am using the smaller cam. However, with the big DSLR  there is the other tension; namely muscle tension in the wrist in trying to support such a heavy load.

A middle ground obviously needs to be arrived at, which I think mFT cams are capable of doing if designed correctly.

The problem with most mFT cams is that in order to look good on the spec sheet, and thereby in my view showing a lack of confidence in their product, or perhaps fear of market forces, the manufacturers plonk a massive LCD on the cams thus leaving very little real estate for better button placement. In my view, with the exception of the slightly larger bodied Panny GH3, none of the mFT cams have any business sporting 3 inch LCDs; that size screen is just too big for the bodies. The back of the EM-5 looks weird, like some portable TV, because the LCD dominates almost the entire rear (leaving the photographer's buttons squashed up to the right hand edge). In fact a glimpse of the rear of the EM-5 gives one the impression that the buttons to the right were just an afterthought.

Just my thoughts on the matter. YMMV.

Regards,

plevyadophy