I've clocked about 30 minutes, so here are your impressions:
First thing that will strike you if you've played SOTN is that Konami has created almost no new assets for this game. The music is the same, the sprites are the same, the map is practically the same. (The character portraits are sufficiently high rez.) If you love SOTN as much as I do, this is a great thing, but others may feel it's lazy.
Think of the map system as Puzzle Quest, except on the map from SOTN. You move from room to room, some rooms are locked off until you have an appropriate item. Moving to a room may get you into a random encounter, you might find an item, or nothing could happen. You can still hit random mobs in rooms you've been in before.
Battle plays a bit like Puzzle Fighter: you're dropping paired gems down a well and you want to match 3 (doesn't have to be in a straight line). The pairs sometimes include inactive pieces which you have to match next to to activate, but that makes chaining pretty easy since you can buffer in pieces to break. There's no "giant gem" building ala Puzzle Fighter. Making chains sends inactive blocks over to your opponents. The sort of twist combat here is there's a timer at the bottom of the screen, and when the hourglass runs out, both players take some quantity of damage (HP meter at the top) based on how empty their playfield is. So the goal is not to necessarily create giant chain structures (unless you can tank the damage) but to balance an empty playfield with flinging shit at your opponent. Note that a full playfield does NOT kill the other player, but does "a percentage of damage" and knocks a few lines out of the bottom. So filling their screen is likely to kill them but it's not instant death. (There's also a type of block called a "Blood Block" which is apparently a wildcard, but I haven't seen them yet.)
You can also use items or magic during battle - there's a "quick cast" button that lets you assign four items or spells to four quadrants of the screen. I only have healing items so far so can't tell you what spells are there.
Battle controls: Tap to rotate, drag to move, swipe to fast drop. Controls work pretty well and there's a sensitivity slider in the settings to change how much of a swipe you need to fast drop.
Character building: oh man, there's a lot to do here. Strength increases your attack power, so more damage per hourglass flip. Stamina increases your maximum HP. Intelligence increases your maximum HP and increases spell effectiveness. Luck influences the color of block spawns for you AND your opponent. Then there are five affinities, one for each element/color of block - leveling those up will unlock you spells at various milestones (first one is level 5). Like PQ, you get a batch of upgrade points per level and you can distribute them however you want.
IF THAT WASN'T ENOUGH: 7-slot inventory system, with item sets that bestow bonuses. An achievement system called "Honors" which will give you additional items. A card system, which does little other than unlock Honors (as best I can tell). The save rooms on the SOTN map are now "Safe Rooms", which restore your HP, let you shop, and let you warp between previously visited ones. Facebook integration for leaderboards. And Arcade Mode, in case you don't have time to dig into Story Mode.
One last note: I'm playing on an iPad and it looks great at 2x. So iPad owners shouldn't wait for a native version because I don't know what the point would be.
So basically it's Puzzle Metroidvania and you should buy it immediately.
STRONGLY RECOMMENDED FOR: Puzzle Quest fans, Castlevania fans, Metroidvania fans, people who like fun.