Game is out for general release now. Tinkered with it briefly last night.
The voice acting is hilariously awful. This is some mid-90s PS1 game level stuff.
Graphics are nice and feel appropriately Metal Slugy, though there's a lot of the weird stretchy static image animations in it. Same thing that's in KOF: All Star and other mobile games. Looks cheap.
Gameplay, just from the first few stages, feels very much like a "mobile" Metal Slug with autoaim (optional, but a pain without it) and having to get used to not having buttons. Bombs regenerate instead of being a static amount. You can get two levels of weapons now beyond the pistol, which includes one you equip and start with (which also have limited ammo), and the ones you find in the levels like normal. You can do "ultimate" skills that have varying effects. Bosses can have weak points you can exploit by firing at them from different angles.
More to come. No P2W stuff yet, but I'm sure I'll hit that wall soon enough.