Though there were a lot of waves, it really wasn't that bad. What you see in the demo is almost as bad as it gets. Honestly, the demo almost pushed me away from the game as I anticipated a ridiculous amount of enemies would follow deeper into the game.
What won me over was the variety. Different setting, nailing pirates from the jet ski, from the jeep, from a boat, as you were running away, and even the quick time sequences were used in good taste.
If you have a PS3 and still haven't played this game, just give it a rental.