docx is a horrible idea.
In newer versions of office, docx is the default file format. Here's the problem: it doesn't open up in old versions of office. Yes, they have a plugin, but your average person doesn't know where to download it and when I tried it, it still didn't work on the document I was trying to open.
I feel bad for IT guys and the techy-person-in-the-family who has to try and explain this to untech-saavy people. What were you thinking, Microsoft?
Sure I use Photoshop to edit my photos, but I would never send people photos as .psd files. I get that you're probably doing something to advance the office file format, but it it really worth making Grandma's recipe file completely unreadable to 90% of computers? What kind of bells and whistles do you need for a recipe?