Finished God Eater Resurrection with all the achievements (the collect all other achievements one is apparently bugged, but I guess that's why SAM exists).
I had a ton of fun with the game, but it's also definitely not without its faults.
Gameplay
It's very fast-paced, and missions usually take between 5 and 10 minutes, some are shorter if you're good and others are longer. You can always switch between melee and ranged, can dash-evade and block with all set-ups. Weapon categories are varied enough with how they play and differ in the types of damage they deal - different enemy parts are weaker/stronger against different damage types. It's mostly important for bond-breaking, but not terribly important if you just want to kill things.
I'm slightly dissappointed in how Guns get more and more important the further you get in the game. It gets really easy to refill your Oracle gauge (*cough* The Cornix devour is completely broken *cough*) and skills to reduce bullet costs. Thankfully I've heard that God Eater 2 does that better.
The game isn't really grindy at all. You usually have enough materials by just doing the missions available and there's also the option to craft missing materials.
Difficulty:
It's really easy for the majority of the game. There are only a handful story missions that are actually challenging and it's only at the end where missions are actually more often difficult than not. Apparently it's the easiest game out of all the God Eater games and their versions, because the 'old' content isn't really balanced for the new additions. Predator-styles are fun, but they and control units can easily become completely OP.
It's really only the Resurrection content that gets noticably more difficult and most of the Challenge missions at the end are fantastic. Not only because of how challenging they are, but also because the missions themselves are more interesting. There are missions where you have half a minute to precision-shoot down some weak enemies. There are missions where you have to fight hordes of weaker/medium strong Aragamis while a extremely strong Aragami tries to murder you. There are missions where you have to survive until the time limit is over and try to gather and kill as much as possible, etc.
Monster variety/pacing:
I think the variety is decent and new Aragami are introduced fairly regularly. There's only one stretch where it gets really repetitive and mostly only throws Fallen versions at you, which are essentially color-swapped versions of Aragami that have a different element, look slightly different and have slightly stronger attacks. That part can really drag (I think it's Difficulty 4/5), but it never gets as bad as that again.
What's really neat is how you can see how enemies got more interesting and better designed with each version of the game. Breaking enemy-bonds is essentially only relevant for drops and reducing defense at first, but later on there appear Aragami where there is more to that. The Hannibal has scales on its back that are its weak point - but if you break them it gets a power-up and a new move. The Venus has a lot of bonds you can break to seal off some of its attacks. Breaking the Calligulas 'claws' vastly reduces its attack range, etc... Some really cool stuff.
Story:
Was actually way more entertaining than I thought. It's anime as fuck and can get really cheesy at times, but it's also really engaging at others. The second story arc was great.
NPCs
Something I really liked about the game. Taking them on missions with you earns them AP you can use to unlock more skills - most are passive buffs, stat increases, new bullets ore skills that affect the rewards after a mission. There are also a number of small 'cutscenes' for each NPC that can trigger after a mission that simply have you spend some time with them and give some characterisation.
Speaking of characterisation, the personality of the NPCs also reflect in their behaviour during missions. Like Annette and Frederico just stay and do nothing if you get to far from them, like the rookies they are, or how Alisa is very good at making sure your Burst is always at level 3, or how Kanon likes to shoot you in the back.
Music
Soundtrack is great. I like how most of the songs have a number of different versions depending on the map and which Aragami are in it.
Probably forgot a couple things, but that's already way too many words