Is typing comfortable with a standing desk? Every time I've used a computer at standing height, it's been a little uncomfortable, but they certainly weren't tailored to my height.
You really need one customized for you. It's probably worse to have a misconfigured standing desk than it is to have a correctly configured sitting desk.
Typing at a standing desk is comfortable if you get the height correct for your body. And for me it is important to have a riser at the front of the keyboard, like this [1]. My arms are angled close to 90 degrees, but pointed slightly downward, a keyboard flat on the desk would put far too much stress on my wrists.
I use this one that I built for $22: http://iamnotaprogrammer.com/Ikea-Standing-desk-for-22-dolla...
Love it. Use it every day at work, and days when I have to sit all day (Traveling, in meetings, whatever)... I feel AWFUL at the end of the day.