The good:
The loadouts allow you to have different play styles. The weapons clearly have advantages to each one with their mods and fire rate etc. I like this because I feel like games like COD get bogged down throwing a thousand guns into your options and 95% of them are exactly the same with a different skin. This game really feels like it has cut the unnecessary trimmings and just stuck with what you need. And this extends to special abilities and ordnances as well. You pick your play style, (run and gun, stealth and accuracy, etc) and you play. So little hassle and you don't end up spending days trying to get two mods you want out of forty useless ones.
Titans are fun. Even if you don't feel like getting in a big mech at the moment you can tell it to guard or follow you on its own and just be a big distraction while you do what you want. They are clearly an integral part to gameplay and teamwork but you are never forced to use them directly and you can do serious damage as a pilot if you are smart about it.
Balanced gameplay. Titans never feel all powerful. They can be taken down by a smart pilot. Same goes for pilots, if you are dumb titans will crush you over and over. You have the ability to do well either way. Guns are balanced well as well. I never feel like one weapon is all powerful. Suit your play style and pick what you want.
The mix of titans and pilots makes gameplay change throughout the match, which is fun. It is less rinse and repeat than other games like COD.
Jumping off walls is great. Moving around the maps is refreshing with a double jump and wall run. Makes being the little guy entertaining and also more survivable in a game full of giant mechs. This also allows more interesting map layouts.
A good handful of fun maps. You have the typical ones that could work for any shooter, and you have some that only Titanfall can play. There are attractive locations with different looks to them aside from some generic maps.
The bad:
The story mode is not really a story mode. It's an interesting attempt at making single player different but I did not really enjoy or care about the plot. Playing 'campaign' through exactly the same multiplayer matches did not do much for me and I will not play it again now that I have the unlocks from it. Either do a serious story or leave it out. Half of a story mode is only a waste of time.
The AI players are more annoying that fun to kill. Most of the time you can run right past them and they wont even hurt you. Although randomly once or twice I have had an AI go rambo on me and kill me out of nowhere when I was not paying attention. It seems the AI should either be smart or not in the game at all. Right now they are just an annoyance.
The smartpistol. This is the only weapon that should not be in the game. I understand no other game does a gun like it, and they want to be different, but that is because it is for no-skill players. Screw them. They can go play non-competitive games. There is no reason you need to put an auto targeting handgun into a competitive shooter. If you are head to head the smartpistol will be too slow but if you don't see them first you have no chance it's a one shot kill. I have never used it because I refuse to but it is the most annoying thing in the world to be shot by someone using it.
Despite these negatives I still enjoy the game as it is different from other shooters. I don't feel like I am playing COD so that makes me happy. I do hope the game continues to grow though and refine what they have.