I think I'm in the minority with no here. But I'm with Tara here: I don't find writing fun, but I find it fun to have written something. The fun part, in other words, is when it's done and I can read it and so can other people. Thinking up ideas is also fun.

The process of writing itself I find sometimes cathartic, sometimes difficult, sometimes fascinating, often an interesting challenge...but I wouldn't say fun.