The first week of any competitive multiplayer is always the most tumultuous. A large influx of new players of varying backgrounds, with different skill levels, and different aptitudes to learn, get better, or otherwise exploit the game for their own means.
Injustice is accessible but also unforgiving at times. Sometimes you can spam a move and effectively shut someone down. But the strictness in stringing together combo moves and specials are not lenient at all. After ten matches of crushing defeat and ten matches of enlightened victory, I can start to see how the meta game for the initial stages of launch will be.
Interactive items are also powerful and more than you think. All interactive item attacks are unblockable, which makes them an important subject to learn and counter, lest you lose a large portion of life to them. You not only need to pay attention to the spacing between you and your opponent but also your opponent's position in the stage. If he's moving backwards deliberately, chances are he's trying to lure you into an environmental hazard. I've played a few matches where a character intentionally moved away from me, despite my repertoire of projectiles. All in an obvious attempt to have move in range of a car or statue so they could smash me.
It's this tactic that makes stages like Metropolis so popular or Atlantis so favorable. On Metropolis, there are an infinite number of hovercraft that respawn no matter how often a power character may throw them. This makes the stage favorable if the player relies on brute strength than player skill. Atlantis by comparison has only a few interactive items which stay destroyed after being used.
Most interactive items have set trajectories when used depending on the character. Gadget characters will cause debris from an explosion to move downward. Power characters may chuck them at a 45 degree angle. Most items can usually be avoided my jumping though. Flash can even phase through these attacks to give you an idea on unique character options. By far the most important thing to know is that using these items have a long start up period. If you find yourself being maneuvered into position for an item attack, remember that you can also hit them out of their wind up period. Usually this means using your trusty reversal move to knock them down.
Grappler characters are still in Injustice despite the superpowers. Rather than focus on making their throws fast, they often times have armor. It fits though because this game isn't about speed but spacing. But it certainly changes the idea of fighting grapplers in Injustice since we're used to pure keepaway from throw range. Instead, characters like Bane or Solomon Grundy have command throws that cause them to move forward with armor. Reacting is less about staying out of range and more about reacting to the actual action.
Another powerful character to watch for is Raven. Her Singularity attack lets her instantly reach out a set distance and crush her opponent into a ball. It doesn't matter if they're jumping or crouching; if they're not blocking, it'll catch them. Raven is one of the few characters to demonstrate a catch type projectile that simply hits everything in front of it. Hal Jordan, the Green Lantern, has a similar power in Lantern's Might, which makes midrange for characters of similar movesets dangerous when they can control space.
Overall, space control and zoning is somewhat prevalent and especially hard to adapt to due to the large size of characters and uncancelable dashes. Avoiding unnecessary damage from zoning is difficult since movement is strict, but chip isn't a big deal either. All moves do chip just like in Mortal Kombat, but just like MK, chip damage isn't a terribly large factor to losing, at least now. Chip can build up, but it's almost impossible to keep someone out the entire match and expect to do win with only chip damage. The amount of chip versus actual damage is different from Ultimate Marvel Vs. Capcom 3 where the amount of chip damage being dealt is high and significant to most zoning strategies. Zoning in Injustice is more about frustration and gradual damage rather then total lock down. The frustration is what allows zoners to catch sloppy players with clean hits. But if someone were to stand back and block all the hits, it's not likely to build any meaningful damage.
The game is still building a community though. There is no clear dominating of character selection. From what I've seen, even Bane and Doomsday have initial niches and Deathstroke is certainly popular but not dominate. It'll probably take a month or two before we see a clear picture of how the game will develop.