I have been doing this for about a week. I don't actually have a standing desk though. I just put the 24 inch display and my small mechanical keyboard on top of my tower cabinet (Which is already on a table). This set up places the display at my eye level and the keyboard at just below chest level. So I don't actually have a place support my hands, and I just go 'hands down' after typing something. And typing on the keyboard at a little below chest level feels really great. Because you don't have to bend your wrists up, while typing, as you would need to, if the keyboard was a bit lower (as shown in the pictures in this post).

It actually feels great. (I have a chair on stand by though). The biggest advantage I can see is that, it is easy to take a break and move around, when you are already standing.