I bought it a couple of days ago,it's really good. I never played any of the Streets of Rage (this got me interested in the series tho, so I bought the steam ports of 1 and 2) so didn't went with any kind of fan expectactions and I have to say it's a really solid beat em up. It's a bit too long, almost 2 hour to finish a run, but mechanics and general design are good. It does a lot of little things to try and modernize the genre, but does it smartly. It has a campaign mode where the game save after each level so the more casual audience can play strees free and then it has arcade mode that forces you to 1CC. Moreover the campaign mode is also relevant for the more hardcores as it pretty much works a score chaser mode with a pretty solid scoring system. So yeah, an "old school" game that actually does accessibility right instead of just dumbing down the experience. Other that that it fixes one my main gripes with the genre by making enemies wall bounce instead of disappearing outside of the screen and wasting your time.
Mechanics wise, for what I can see, it's similar to SoR 2 with basic strings, blitz attacks and directional specials, plus a super. One cool thing is that specials don't run on meter but instead spend some of your hp, you can then hit stuff to regain it so you can be pretty liberal with them if you know what you are doing.
One flaws is that movement speed is generally slow and only some character can run or dash, but considering how the levels are paced is not a big deal and you can also use some of the specials as movement options.
If any of you has it on Steam hit me up for some co-op.