Following his article about Glock safety Rob has written an article explaining the differences between the safeties in the Glock and XD.

If the Glock firing pin is partially retracted and the Springfield XD is fully retracted we could draw the conclusion that the Glock is half-cocked while the XD is cocked and locked. Both will fire if there is an accident. Both have safeties in place to prevent this from happening. If the only unique safety on the XD’s is the grip safety, how does it work? It looks like the grip safety on the 1911, but it definitely does not quack like the same duck.

More here.