After over 20,000 miles, my experience matches gonavy's. I do see some IMA benefit in stop and go at speeds under 40. IMA will "volunteer" (I don't have to "punch" the accelerator to "call" IMA into play), and ECO will stay on, the best of both worlds--3 cyl plus battery assist. And Autostop is very beneficial, also, as well as being quiet....

My daily commute (80 miles round trip) includes a couple of hills. Several thousand miles ago, I tried IMA for the hills--ECO goes off, 6 cylinders go on, rpm goes up, and IMA helps; I learned to feather the accelerator to keep IMA on for the 30 seconds or so of ascent, maintaining near limit speeds of 60 mph. Same hill with ECO strategy: keep ECO on as long as possible, driving with load, slowing to 45 by the hill crest, eventually using 6 cyl but no IMA, keeping rpms as low as possible. Always better mpg with the ECO strategy, but not always possible with a dump truck on my bumper.
Lewis