Keep in mind this is Alpha, so there are things that could change (such as the AI, which I talk about below).
General consensus is that most think it's a blast to play. A lot of people seem skeptical about the technical performance (game looks ugly as hell in this Alpha Test, but someone at Respawn said it was only 25% of the texture quality, and that the final build is 75% better then what is in Alpha). There is some skepticism about AI and how it's used (in every match, there is set of AI that spawns on each team called Grunts. They respawn constantly throughout the map. They virtually serve no threat, and you can take down 5 of them at the same time without even getting shot once. Their sole purpose is to give you points, which then speeds up your Titanfall. They add an element, in terms of players and teams wracking up points to get their Titanfall quicker). So there is some doubt about the AI, and how they work. Some feel they are used to make players feel like they are doing good, even when they have a bad game (I personally disagree). But overall, I would say most are having an a blast playing it. I know I had a lot of fun today.
It def plays like COD. But it also feels like a natural evolution of it. The way you are able to traverse the landscape changes everything. It means that the game is no longer about twitch shooting, but requires more skill and more action to battle. You can actually escape from your enemies in this (as compared to COD, which is very much you die, respawn. You die respawn). The Titan battles are epic, and again..just add more overall strategy. It's basically a race to rack up as many points (and as quickly as possible), so you can get a Titanfall.
The Titan fights are a nice struggle, and aren't just over in 10 seconds. So it becomes this thing where you want to get as many Titans on a map as possible (so you want your team to have 2 or 3 Titans so you can overcome battles and take down the other teams Titans). It doesn't really play like Titan's running around and killing a bunch of humans and racking up kills (sort of how Killstreaks feel in COD). There is always that check and balance, because the other team is going to get a Titan. So they are always battling. But the struggle is teams getting more Titan's quicker so that tides turn in their favor in Titan battles.
What feels like COD, is the speed and hectic nature of the game. But there is a lot more things that add strategy to it, and make it different. Maps are more on the medium side (I guess some would say small). The 6 vs. 6 is actually a really great balance. You won't notice it tbh.