This is by far the best feature in 1.5. This capability allows Firefox to update much quicker (which means more people will keep up to date). This is not only a bandwidth saver, and a way to quickly update, but it’s a security enhancement. It makes staying secure easier and faster, which should translate to more people keeping their computers secure.
I wonder if anyone is planning to port this to SeaMonkey or Camino. No clue how much work would be involved there, likely a fair amount. Anyone know if there are plans to spread the updating love?