Street Fighter x Tekken has had playable builds floating around, which I've never been able to get my hands on. I finally changed that, and I have to say I am pleasantly surprised with the game thus far. The art style, while reminiscent of Street Fighter 4, is done differently enough to look fresh. The character models are beautiful, as are their every last animation.
Tagging mid-combo and juggling are a very strong focus of the gameplay, akin to Mortal Kombat's tag system more than Marvel vs. Capcom's. From what I was able to deduce, pressing one of the right shoulder buttons (I played on a PS3 build) during a combo would immediately launch your enemy into the air and switch out to your second character, where you're able to put a nice bit of punishment on your airborne adversary. In the vein of the numbered Street Fighter games, Street Fighter x Tekken felt to be more about controlling pace, timing, and execution, especially in comparison to it's Versus series brethren.
The Tekken characters felt a little awkward in the Street Fighter universe, as it takes some time to readjust to universal hadokens and shoryukens as opposed to long strings of attacks. My Tekken tactic of mashing the kicks did little to give an advantage as Hwoarang. Regardless, it was great fun latching on and distributing flawlessly rendered ass-whoopings with my favorite characters from both worlds.