I just finished the game last night. I liked the game and I enjoyed it a lot. However there are a few things I didn't like that much.
Rage is a single player action game. Don't expect COOP and don't expect to have a lot of weapons to farm (its not a looter either).
But lets stat on what I liked:
-I liked the world, its a big enough world with different environments and things to do.
-I liked the combat, the abilities are cool and fun to use in combination with the weapons.
-A lot of action
-Different vehicles
-Good looking game
-I played the game in my first language (Spanish Latinamerica) and its pretty good.
-You can complete the missions in the order you want.
What I didn't like.
-For me the biggest downside was the plot, I think the rage universe has more potential, there are not good characters (bad guys) in the game.
The plot is very simple, and don't explore anything new, It is not interesting at all.
-There is one bug almost at the end of the game where you cant call the tank again if you do fast travel or lost it for some reason, so once you get the tank, go and complete the last mission, you can complete whatever is left of the game afterwards.