I have a desktop, a netbook/laptop, and a Kindle Fire, and I prefer doing everything but reading on my desktop. The screen is bigger, the keyboard is easier to type on, and it has a real mouse - that's a big one. I hate, hate, HATE the touchpad mouse. But sometimes I have better luck writing on my netbook because I can take it wherever I want and because I get less distracted on it - I don't have any music or videos or pictures saved on it and only a few websites bookmarked, and it's not as easy to surf the net on it, so I don't do it as often.
I can't imagine writing on my Kindle, let alone my phone! Actually, my phone might be slightly easier because it at least has a keyboard instead of a touch screen, but just texting or tweeting takes long enough that I can't imagine how slow I would be at writing. I'm sure you get used to it, and your phone's probably better than mine, Tracy, but wow... I give you props for that!