I'm on the middle of this argument. They were able to catch the guys by clearly identifying them from like 1000 different angles, probably more cameras were able to track specific movements such as ATM's and private CCTV cameras. If it could save lives and the tax payers of Chicago pay, go for it.
On the other hand, I just got back from HK and you couldn't walk a street without a camera. I thought I was the guilty one, but it made me conscious enough not to break their strictly enforced laws (that we see as nothing).
If terrorists knew their every movement was being watched, would they still do it? Depends on their agenda, but I believe yes. Would a criminal still rob, steal, rape, kidnap, etc? Likely, but I believe in much lower rates.
Overall, would it be worth it?