For general writing, I would not usually consider using a pencil. I’ve only ever used one when I thought that I may need to erase something. I wonder if the Pentel Twist – Erase Mechanical Pencil will change my mind.
I can see the obvious benefits a mechanical pencil has to offer over its a standard wooden cousin. No more hassle looking for a sharpener, or trimming with a sharp knife, as I often used to see my granddad do (not recommended, especially if there are any young readers out there).