did Mirrors Edge ever get an OT? (i must be missing it) edit: found the OT by searching catalyst.
is it any good? semi open world sounds... eh.
The open world works brilliantly with the Mirror's Edge formula and anyone who says otherwise is straight up wrong.
The main campaign missions are very similar to the first, linear with loads of cool setpieces, the only difference being you start them by running to a start point in the world. The story is pretty forgettable but it serves reasonably well in pushing the game along. Basically it's pretty much more of the first game which is great.
However, alongside the campaign you've got this massive playground of an open world. It is filled with so much content. People who complain that the side missions are boring and a waste of time are being ridiculous, that's like complaning the races in Forza Horizon are pointless filler. Time trials and races are the bread and butter of Mirror's Edge. That's what the game is all about. You've also got puzzle and platforming missions, user created races of various types, leader boards etc.
If you like the gameplay in Mirror's Edge then absolutely buy it. Catalyst builds upon the the first in some good ways and gives you a wealth of content to play with. It's fantastic and massively underrated.