Just beaten this, thoughts below:
+Good graphics and performs really well given how good it looks
+Generous checkpoint pacing, never had to repeat long sections
+Generally a solid feel to combat, movement, weaponry etc
+Nice throwback to traditional style of FPS, essentially moving point to point intertwined with combat, so you rarely feel like you don't know what to do next
+Forgiving platforming sections, focusing on making you feel like a god rather than punishing you for mis-timed key presses etc. I like that you can fall slightly short on a jump but if you are in contact with the side of a ledge you can spam spacebar to clamber up it.
+A few interesting level designs, such as when you climb up and a combat arena builds around you, or the time-travel level
+Sections with significant allied support are great, albeit used a bit too sparingly
-Boss fights seem too easy, I think the only one to kill me more than once or twice was Viper
-Looking back you don't actually do THAT much combat, maybe 300 kills or something like that?
-Jumping / puzzle routines feel a bit like a missed opportunity to blend in some more complex chained sections, maybe something in the Portal 2 mould. Shooting a switch mid-jump is about as complex as it gets.
-Felt like the characters could have had more lore built around them, I found myself not really having much attachment to the Militia nor really felt like I got to the stage of harbouring any emotion about the IMC bosses I was taking down, they were just another cliche
-Ending seems a bit lame, I was waiting for some sort of grand finale fight and just got what basically equates to a highly predictable interactive cutscene