Pencils are great, but ever since I started using whiteboard notebooks, like this[1] and this[2], I haven't looked back.
The pens I use now take a few seconds to dry, and so would probably be a problem for leftys. For me, they work great, and I only occasionally smudge something.
Here[1] is a scan from today. This page (and the entire notebook it comes from) has been fully erased about 10 times. (I scan in all of the pages, and then wipe 'em clean once I've filled the notebook).
Wiping can be a bit more time consuming than with a normal whiteboard. The manufacturers claim all sorts of things will work to wipe an entire page, but I've found that for best results you need to use cotton balls + pure acetone.