If it plays anything like Smash, it'll be fun, but at the same time, everything else about the game will really kill the enjoyment.
It's a much faster than the recent offering of Smash Brothers. The stages are also crazy interactive. There are your calm moments where you and the others basically duke it out, but eventually a hazard pops up, or there's some object in the stage that you can interact with to turn the fight in your favor. Several stages also do transitions. And proper transitions mind you, none of that Fire Emblem crap you saw in Brawl.
The sewer level for example. One moment you're fighting in the sewers when a torrent of water pushes all players into another area with platforms that push you away from falling water, and a giant alligator that guards the bottom and pops up every now and then to take out any unlucky S.O.B still at the bottom.
I didn't get a chance to learn much of the move sets yet, but it's pretty simple to get in and have fun, and if you get caught in some annoying juggle, you'll be given a chance to break out from it and counter attack. However, there are some problems where you could end up being cornered by a character if they kept spamming a certain attack. I believe there was a counter to the situation but I didn't have time to properly try it out. There are items that enhance or give you special abilities such as the ability to breath fire to further increase your arsenal attacks.
The game doesn't have the same knockback like system in Smash Brothers, but that's expected with the vitality system. You want to pummel your opponents, not send them flying. However, this is actually a welcome benefit since now you'll be spending a majority of the time fighting rather than playing mind games to try and launch them out.
This game is also visually stunning. There's so much fancy effects going around, and it helps that the stage actually helps in the fight. So not only is it nice to look at, but you can also use it as a distraction or an obstacle against your opponent. I couldn't really judge the music or sound effects of this game, didn't really pay attention to them.
Overall this game is very fun and I'm looking forward to the final release. Still hate those god damn Rabbids though. (Although, they were not playable in the build that I tried.)