More thoughts? Sure.
I like to upgrade after a couple of cycles, so there is a significant improvement that's worth paying for. (I also tend to do this near the end of the product cycle, when prices are down, explaining why I bought a new 5D2 and a new GH2 last year...) In this case, the improvements in the sensor are enough that I would want to upgrade, if it were me.
You are already noticing the user interface problems, so that's another reason to upgrade.
Given the product cycle, I wouldn't expect an OM-D Mark II in the near future, and even if one were announced, it would likely be a year until it was widely available. You could be shooting with your OM-D for that year.
The 45/1.8 is a wonderful lens. The 12/2 is very nice, though I ended up with the Panny 14/2.5 to start (good quality, 1/3 the price), then bought the 12-35/2.8 zoom which I quite like. Given the rebates on lenses that you want to buy anyway, look it them as a $300 discount on the OM-D, making it $650 -such a bargain!
I'm tempted just for the $150 discount on the 75mm lens...