Olly OM-D E-M10 Good idea?

In terms of real world functional performance the E-M5, E-M10 and E-M5II are all much the same, the E-M10 and E-M5 II share newer firmware which still has upgrades, the E-M5 I which I have has older firmware, which means no updates. They're all about as fast as each other, which means slow CDAF based tracking which is not particularly good particularly at this stage given the other cameras out there such as the G7, GX8, GH4 and E-M1 which all have faster auto-focus.

The weather sealing? I thought I'd use it at first but it never really gets into a situation with weather in Australia where I can't shoot shots, it might be different in New Zealand due to the very different weather across the ditch.

You pick up focus peaking and zero second anti-shock though which at this stage? It's worth it... The E-M10 is a great camera provided you don't need a battery grip or AC power adapter, which also comes in the grip of the E-M5 and E-M1 series cameras.

What you lose is as I said a powered grip and weather sealing, you may not need these though and you lose some ergonomics. I find the E-M10 too small, it's smaller than the E-M5 and when you put a grip on it, it doesn't actually change the dynamics of the camera as none of the buttons move, the E-M5 with the grip on the front of it reassigns the shutter button and either the aperture control or shutter speed dial. The E-M5 II does this by default and its much better, as its not just a pass-through to the button from the existing buttons on the camera. The E-M1 gives you ISO controls on dial which is even better again.