[steadicat]

And there are plenty of disadvantages related to the drawing.

Most annoyingly, the fact that you can't alt+drag or alt+nudge (arrow keys) to duplicate an object. For me that's the single biggest time-saver when doing wireframes and mockups. Otherwise you spend a lot of time repositioning and realigning pasted objects.

Most desktop apps get it right. I've yet to find a web-based app that does.