Hi, Kambiz
Here's another idea for simplegraph: When you insert a couple of nodes and move them into negativ coordinates (the upper-left corner of the component), they are "lost", because no scrollbars appear. Of course you can mark all objects and move them by keyboard into your view. But for many users it would be a lot more comfortable, if scrollbars are shown for nodes with negativ coordinates too.
C.U. P_G