It really depends on what you are doing. If you're planning on getting any decent shots of a rider in low light that is behind the boat, you'll need strobes to get a decent shot.
For Christmas time sitting around the tree, the onboard flash works fine.
For wedding photography, you'll need an external.
For Glamour, you'll need an external, and an off shoe camera cord ($50 at Amazon.com)
It really boils down to what you want to use it for. Personally I could not imagine not having my external flash. I use it very frequently even in the middle of the day.
Using the External Flash with the offshoe cord: http://www.swamistudios.com/photoshoots/061007%2Dswami/slides/IMG_0382.jpg
This is a shot with no flash fired. http://www.swamistudios.com/photoshoots/061007%2Dian/slides/IMG_0397.JPG
So even in the middle of the day, I find myself using it. You couldn't do this with the onboard flash because the lens I used is too big and it creates a shadow on part of the shot.
Also: can anyone tell me how to post images on this forum? HTML code didn't do the trick.
(Message edited by Swami on October 10, 2006)