I've shot extensively with the following cameras, each of which I've owned: 1DsII, 1DsIII, 5DII and 5DIII. The 1DsIII was better, took better pictures, resolved more detail, shot good quality at slightly higher ISO and had less failures (see mini firewire port) than the 1DsII. The 5DII was almost as good as the 1DsIII in most respects (except for build quality, of course, where the differences were "major"). The 5DII did have a tiny higher high ISO advantage over the 1DsIII and could also shoot HD video - a couple of usefull advantages, but was really not in the same ball park for pro stills photography.
After testing the 5D3, I abandoned my 1 series Canons altogether, as I don't shoot a lot of sports/action, nor
do I shoot in a lot in inclement weather, the only two reasons I can think of where the 5DIII falls much short of either the 1DsIII or 1DX, much less the earlier 1DsII.
As far as the 1DsII is concerned, it was a great camera in its heyday, and I happily made a lot of money with it. However, it is clear that the 5DIII camera is far superior to it in all but a very, very narrow set of shooting conditions. You may feel very comfortable with the 1DsII, but, unless your testing ignores about 3/4 of what you use a camera for, you will never see better results from the 1DsII than the 5DIII, or even from its successor, the 1DsIII.
Let me put it this way, if like your 1DsII that much, then by all means keep it. But, if you were to give the 5DIII a little more time, I'm pretty sure you'd come to the same conclusion I have: the 5DIII is a superior camera in almost every way.