This is a pretty thorough overview of the XD-S. This particular concealed-carry pistol was affected by the recall, and Justin Opinion compares his shooting experiences pre- and post-recall fix.
The fixed XD-S pistols have a slightly heavier trigger that is by all accounts smoother with no stacking and a cleaner, more predictable break.
The fix is standard on all XD-S pistol from now on, so if you tried one when they were first launched and thought that the trigger was too spongy for your liking you might want to give them another chance.
You can spot post-recall XD-S pistols by the pin in the grip safety.