Pros:

- Great concept
- Chance to get evrything that you want
- You need time. You have no it. You must build "exit". But before you must survive

Cons:

- That would be great like a survival map (maybe not instead this co-op)
- Playing with bots is chalenge. Hardcore. EXTREMLY HARD even on "easy" (they cant use tech tree/build barricades/use machinegun and you fighting almost alone)
- But playing with people is EASY. Well you can play on expert and probably it will be fun)

Conclusion:

If you play with bots you play almost only for building/unlocking/picking up. You must unlock new weapons. You must get weapon for yourself AND for your bots. You must get healpacks for you bots. You must barricade way alone with no support. And when you will get to the rocket you will must kill bots becase they will not go to the rocket.
If you play with frinds it will be easy to get weapon/barricade/way out. That man who will unlock weapons/building can feel safety. And not only YOU must do it.
Play with friends for fun time or play with bots for HARDCORE.