This was a "cross"over meant to be.
The gameplay and mechanics are pretty solid. It's at first similar to Street Fighter IV, but has a little mix of Tekken Tag (rules in the match) and even some Mortal Kombat (for tag cancelling). Yet, at the same time, it's a new type of mechanic and gameplay entirely. Let's start with SF. Many of the bread and butter, mix-ups, and common combos remain. However, juggling, wall bouncing and ground bouncing extends combo possibilities, which is great. For the Tekken side, it's actually not bad. A lot of people feared that putting them in a semi-foreign dimension from theirs would be a huge disadvantage. Capcom knew what it was doing. In fact, with their experience in the EX series, they understood how the 3D world works. In addition, since SF II, there were characters that were given "side-step" moves to avoid fireballs. This idea remained for the Tekken guys. Almost all have a move that not only have them dodge attacks, but advance toward the opponents as well, putting pressure. As I played with King, Hwoarang and Raven, I could easily dodge and punish fireball-trigger-happy people. Furthermore for the mechanics, though the move sets are altered a bit to fit into the SF world, they are not really hard to try out and play with. Also, many still have their classic combos from their series.
Overall, the EX moves are back and more effective than ever. Also, there is a special move that you can charge to either its EX or super arts depending on the length of the charge. What makes it fun is that once again, due to juggling and such, so many paths to finish off the opponent with Super or Cross Arts are opened. The tag features are really fun and easy to use. There's a simple combo into (tag) launcher, and tag cancel from any move. Definitely they are nice setups for devastating combos.
The graphics are a bit more goofy compared to SF IV, though it heavily borrows from that game. Tekken characters don't even look half-bad, but silly nonetheless. The stages are really entertaining. You'll see lots of references and cameos to both series. Also, I like how the stages changes over time during the fights. Makes the matches really exciting to watch. The Super and Cross Arts are really great and dynamic.
The soundtrack is a great listen. Though you can tell it's more of Capcom, there are some good mixes from the Namco side as well. You might be moving your head and body a bit as you go through the menus, play/watch matches, or watching the prologue and epilogue. It's a good variety of hip-hop, electronica, house, pop, opera, rock, and smooth genres.
There is a big variety of modes that makes the game worthwhile. The tutorial feature is perfect for beginners and goes step-by-step. Once you get used to the system, you'll have the Trial and Mission modes to try out. Both are really fun. They help out to deal with many different situations during matches, and helps build confidence in going to a rough match. The most "infamous" features that bothered everyone were the gems. As frightening to the balance of the game as they seemed to everyone…they actually are not really a liability. In fact, they're effective, but not completely game changing. They usually require certain conditions to use them and once used, they're gone after a few seconds. Many are indeed useful like the power, speed and defense. Moreover, it's more for figuring out tactics for players and help newcomers getting advantage over veterans and such.
The pandora mode seem very risky and useless unless you can pull off a desperate or amazing comeback. I highly recommend not using it though. The scramble mode is a lot of fun. It's like a mini-Smash Bros. 2-on-2 with all 4 people duking it out. It's a great feature if you want to get away from the usual 1-on-1. Speaking of the 4 players, that's how many of them, can play the game. Now, constant communication with the teammate is always important, so if you're doing combos together, be on cue for your tags. If it is just you and a friend, you can actually practice together offline….or…online.
The online mode is not bad. You and a friend (not local though) can team up and do matches together. What's the most fun part about it is that you can actually train online with your partner as long as you want until you quit or find a match. Even if alone, you can form a team in the Endless Lobby, which is cool. The only downside is the annoying constant sound glitches that occur during the matches. You'll hear a hit or two, voices cut off during speeches, and sometimes nothing but the music. Still, it doesn't bother match itself, except if you have to mute the TV.
Overall, this game is very good. Great and fun mechanics, unique features, fantastic music, variable modes, and great cast of characters mixed into one awesome game. Definitely a "cross"over that was meant to happen.