John Romero's Daikatana had a bumpy development; people leaving left and right, disputes and people supposedly trying to bring down the studio behind it, Ion Storm. With this in mind it's a little less surprising it came out the way it did, but looking past the faults you can see a promising game that's merely just missing some major polish. When this is in consideration you can somewhat admire Daikatana for what it is, a fast-paced first-person action shooter that's heavily inspired by Quake while bringing some new features into the mix such as the ability to level-up both your own abilities and the Daikatana itself, but the execution leaves a lot to be desired; cinematics are dull and poorly directed, animation quality is poor, the game is graphically dated (using Quake 2's engine) and the game is quite a buggy mess.
There's a lot of interesting complaints about the companions in the game, but in my case I find if you just ignore them the levels often give you opportunities to open a door to let them catch up more quickly which makes cases of them getting lost or you having to wait for them fairly rare. That all said, the AI is still a place of complaint as you'll find yourself getting frustrated having to constantly issue your companions commands and to also ensure they don't manage to get themselves stuck on a ladder or something silly.
With this all said, the singleplayer in Daikatana leaves a lot desired and might not exactly be what some people consider fun. The game gives you a challenge, yes, but sometimes in the wrong ways. The environments however are nicely varied at least and with cooperative play there's certainly some replay value.
Multiplayer is a slightly different story however and actually proves to be a fantastic portion of the game thanks to the many varied weapons featured and its fast-paced nature which seems like a nod to Quake. Some players of older games such as Unreal Tournament, Quake and Quake III Arena might enjoy Daikatana's multiplayer, though you'll have to organise a session with friends yourself as people rarely play.
Overall Daikatana is, mediocre, but it certainly shines in some areas and if you can look past the faults then it might be an enjoyable experience for you.