I do worry that it makes me look unfocused, especially when I do it in meetings. According to a study, however, doodling helps to maintain concentration. I have to say, this is definitely true for me. If I'm in a boring meeting, doodling actually keeps me paying attention. If I don't do it, my thoughts start to drift and I end up miles away. Doodling means that my brain is focused, but only on something simple, so I can still pay attention to what is being said.
I quite enjoy it. You can see that most of them follow similar shapes or themes, although I do occasionally break out different coloured biros for a bit of variety ;)
I still worry it makes me look unfocused though ;)