NEX 6? Any downsides?

Don't buy a camera without having played with it first.  How the camera handles to you is more important than any other criteria.  If you don't like to hold it, use it, navigate its menus, or otherwise find it confusing or troublesome than the camera may verge on uselessness.

I raise that point because different people have different reactions to the implementation of various mirrorless cameras.  Some people can't stand the new age look of the NEX series, their menus, or any number of other issues.  Some people can't stand the small size or the buttons of the OMD.  Some people can't stand the autofocus of the Fuji offerings.

Each "style" of mirrorless cameras fits, or doesn't fit, different people.

Second, while I understand that at the moment you aren't looking for much more than the kit lens and plan to use the camera as a learning tool.  Do give some thought to the next lens or two that you eventually may want.  Different systems do better or worse in this area, and may or may not match your needs.  Sony has a quickly maturing line of lenses, but many people argue that a number of those lenses are not so great optically (here comes the Sony defenders to defend their lenses).  Fuji lenses are almost all very well regarded, but there just aren't very many of them right now.  m43 lenses are plentiful - although some people argue that some are too expensive.

Your next steps in lenses are important because cameras (and kit lenses) depreciate tremendously fast.  This depreciation doesn't mean the camera becomes unusable, but lenses are generally where your money is best spent.

Last, there are some drawbacks to the the NEX 6 that haven't been mentioned.  First, the body itself isn't stabilized - you have to rely on each individual lens and some may not have it at all.  Second, the body isn't weather sealed - but this may not matter for you.  As others have mentioned, since the NEX series is using a bigger sensor, its lenses (generally) tend to be larger.  Pluses are that NEX has probably the best video among mirrorless cameras (although the Panny GH series probably gets more love from filmmakers and such) and the NEX line has focus peaking - which allows for easier use of legacy lenses or other manual focusing activities.

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http://jcharding.zenfolio.com/