Reading about the NEX cameras here has made me regret my purchase.....

Too bad that you only started reading AFTER you made your purchase. If you had started earlier, you could have read how terrible Sony's products are (claimed to be). Often even posted by non users. In fact, the tone of the forum has gradually been improving.

Just go out there and take some snaps, prove all them doubters wrong.

The Nex-6 is  highly capable camera. You'll be happy that you made the switch. You'll see.

Learning quirks? Yeah, there may be some. Ask here and people will help you.

But lugging your D40 around, or its replacement? Neah, there is no gain in IQ, only in bulk. Yeah, dSLR PDAF beats OSPDAF. Big deal, it mereley affects the keeper rate on perhaps 1% of your shots. For the other 99% of shots, the Nex is the winner, usually just because you took it with you!

Take some pictures, post some pictures, seeing is believing ...

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Cheers,
Henry