Why did you buy an X series???

No regrets at all (apart from losing money due to depreciation - if I could afford it, I'd have kept both).  To be honest, the only thing I didn't really like about the OM-D was the posterization I often saw in flat areas of colour such as sky, even at low ISO.  I managed to workaround this by lowering the sharpening and NR in Lightroom and eventually got pretty good results.  The fast AF and IBIS in the OM-D are impressive, but I don't miss them.

Things I like better on the X-E1: the (marked) manual controls, overall handling and lens quality (although to be fair there are also some pretty good lenses for m43, if you can afford them).  Things I miss (very) slightly: good RAW conversion in LR and the tilt screen.

Cheers,

-Steve