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

Actually, cheap DSLRs (like Nikon D3200, D5200, Canon Rebels) have LESS manual capabilities compared to OM-D E-M5. Basically, they have only one control dial (E-M5 has 2), so you cannot adjust shutter speed and exposure compensation at the same time in S (Canon't Tv) mode, or aperture and exposure compensation at the same time in A (Av) mode, and Manual mode is almost impossibility unless you have a lot of time for each shot to change modes and adjust settings (no quick shooting there).

Also, I have not seen them being able to adjust curves as easily as E-M5 which uses the same 2 dials for that.

Also, in terms if IQ, Canon APS-C DSLRs and Sony APS-C DSLTs produce WORSE noise in RAW than E-M5. Nikon APS-C DSLRs with the latest Sony and Toshiba sensors are a little better in RAW, but totally useless for JPEG shooters, producing ugly colors and yellow splotches.

Olympus is good both in RAW and JPEG.