Wait for it to go on sale.
It's not a bad game. I don't hate it. I'm going through it but it feels like a slog, not like a joy. The voice acting is painfully 'present' on some characters, ruining immersion. Some of the written dialogue is painfully bad. The very linear paths are repetitive and make ample use of repeating resources.
The combo moves don't have the joy from UA1 and 2-- you don't feel that awesome 'woah' moment of bouncing a unibeam off Cap's shield. The map areas are so large in places that sprites get lost but enemies are more than happy to snipe you from off-screen with no danger indicators if you use the close-follow camera.
The lack of group level up means you should forget about the team configurations and immediately add any new character to your current roster as soon as you get them. I'm at level 25 and I could bring one, maybe two characters up from Level 6 using the experience boosts I've been saving.
The game just feeels a little joyless. The graphics look 3 years old and the environments are staid and lifeless. The characters themselves look and feel great but it can be a real slog at times with off-camera snipers and stun-locking attacks.