I'm almost done with the campaign, here's some impressions.
Story isn't that amazing, but it's okay. The jokes and script make up for it though. I do like how they kinda explain how secondary Eco is created.
Characters are lame, they really don't have any kind of 'feeling', same goes for the enemies. And there are barely any enemies. Eel, sawbot, firebot, tribot, monkey, dark warrior, dark warrior ghost. The only real enemies who have some kinda meaning are the Dark Warriors.
Thats about it, of course half of the game is just the good ol' J&D formula. However, weapons suck too. There's nothing new! Even the Lobber is just the Plasmite RPG from Jak 3, and in fact, the entire Gunstaff is the Morph Gun. Only worse. I loved how the smooth fighting and gun gameplay in Jak II and Jak 3 worked. I could pull off these fantastic combo's, but now it's just not as smooth.
Same goes for the details, I want my Vulcan Fury rattling sound back ;__;
The Eco Powers are a great addition, they make up for some interesting gameplay and a fun extra for both platform as combat.
Dark Daxter gameplay isn't that bad, it's not 10/10 but certainly okay.
Airship gameplay is actually quite good, I still don't think it belongs to J&D, but it's okay (it better be as it makes up for half the game!). Airships are each different enough, weapons are different enough. Collecting new weapons and mods is good. Only complaint is that the speed doesn't feel right, there's no sense of fast ships raging past each other.
That's it, enjoy?