Currently on my 2nd play through on the Index. Played it the first time on normal and current play through is on hard with Gnome Chompski in tow. The main difference I've noticed is that the Combine and Antlions take a few more bullets. Speaking of segues, ammo seems to be a little harder to keep but the game does a good job of making sure you never run out of ammo with magical spawns. It's nice playing a game armed with the knowledge gained from the first play though but I'm still discovering new things.