Agree completely with Tom. I use the WYSIWYG editor by default to compose my posts. It's easy to use, has decent shortcuts to speed up writing and you can always switch to the text editor when you want.

Markdown is a good enough language to work with, but I also think it's slower to type in Markdown than using the WYSIWYG editor. e.g. It's just faster using CTRL+B vs. typing the ** before and after a word.