Pre - purchase Camera is now also a matter of "taste" :-) or optics / "grip" (haptics), etc. - for any current DSLR camera is to be able to make great pictures - of course it depends on the photographer of what use is the best Cam, if the photographer is good for nothing ...
The processing (housing) is great - there's nothing to complain about ...
For E5 are definitely also Pro Zuiko lenses / Olympus - this is true but for each camera, the lenses make the "music" ...
Whereby, in the E5 Olympus I must say that the image quality has very much improved - the difference for example, E-620 is serious!
So it's really a real development / improvement ...
I use my e-5 mainly with the Zuiko 12-60 SWD - fast & "sauscharf" :-) - to get you started in Oly world that is probably the best and most flexible choice ...
About ISO 800 some other manufacturers are better - but dynamic range, I personally find much better than for example the Canon 7D (and I had a) ...
Perhaps any laboratory tests say something else ..... but in practice shows the E5 super Images / sharp / low / etc. with plenty of dynamic range and depth, think better than for example the Canon ... but that's my personal feeling! - Use the camera as Semipro and had previously had a Canon 1D Mark III and a 7D ... with L lenses !, the transition really no regrets - have however allowed myself also Pro lenses from Olympus / Zuiko to .... here comes of course quickly what to coal together - but also with other manufacturers cost the good lenses much money ... because the market is not much difference ...
I use my E5 on the work in the studio (product shots) and at the customer's site (Portraits / equipment / building) - and so far has me a good piece never disappointed - I use with wireless triggers an Elinchrom studio flash system as well as 2 Metz 58 AF-2 China and several flashes ... and the results are just as good as before with my Canon ... it has at least not yet a customer complains ...
Privately, I am a lot in nature so that the road - here the great weather protection has its benefits ... and here she has never let me down ...
Compared to the Mark III the E5 is handy and the swivel screen gives me in tricky positions, the necessary freedom of movement ...
The display I have to especially praise - I had never where I could see the picture so well already on the screen, a camera - no nasty surprises on the computer after the shoot ... color / sharpness ERC. is really represented very accurately (authentic) ...
So if you can do without ISO 3200 (not just regularly photographed concerts) can be happy with this camera easily .... Is a matter of taste - you can definitely super picture taken with the camera and the video function is okay - have already two small videos for customers turned so ... Super - but unfortunately only ... here HD720 Full HD would of course be even better (better) :-)
But maybe I'll get for the new PEN and NEN Lens Adapter :-)
Have fun - and only then write test :-)