Bought the game last week, and have been having quite a bit of fun, so I went ahead and purchased CAU yesterday as well. I'm surprised they let people have access to the crate missions without buying the DLC, as it didn't add up. $25 is too much for the part of the DLC you unlock, but it would have been reasonable if half of the update wasn't free. (Aka the Crates)
The crates are fun, the working together is nice, I like the way they implemented the Bronze/Silver/Gold/Platinum, with a 25/50/75/100% chance of getting a car fragment. I think they could have done a better job with the Bounty system, the on-screen 'targets' are too big, and more distracting than they are helpful in their current state. The blue-line that tells you where to go is fairly glitchy, the 'start' screen remains on the screen for far too long, and is in your way since the mission starts immediately, and often times a turn is required before it fades away.
I can't say for sure, but it feels as if the difficulty scales with the amount of people in the event. Playing Solo, I can do any of the crate missions, without ever needing to use a single 'ability'. When people start joining to 'protect' me, it seems as if the amount of AI cops are doubled, which is fine, as personally I think these events are far too easy for the person leading the run. On the other hand if you are trying to assist, you're given a rather difficult task of trying to navigate the endless chaos of the person you're trying to 'protect' which is far harder than just delivering the crate. Making your way through traffic, and countless wrecked or emp'd cop cars, while trying to follow nothing but an arrow on your screen, isn't simple. I think all drivers on the 'delivery' side should see the line, to know where the crate is going. On the inverse, when you join someone else's started mission, you are at the mercy of their skill level. I'm only a week into the game, I'm by no means anything special, but I was rather disappointed in some of the people I was paired with, as it was multiple failures for seemingly blatant poor driving skills. This is a double edged blade though, as last night, I noticed a group of 3 driver following me, and waiting for me to start a mission, and eventually inviting me to their crew to continue 'assisting' me, as I bounced around knocking out all the gold crate missions.
As a Cop, you still have to upgrade your car, which I'm not really a fan of. I was hoping to jump in and go arrest some people, but the 717 piece of trash they start you with, isn't going to cut it. Saved up some money, bought a Lambo, but still, in order to keep up with everyone's 1497 Street cars, I had to go grind some parts before I could really compete. I expected Police cars to be ready from the factory, but it's not a deal breaker. As a cop... you are in a very similar situation to the 'protectors' I mentioned above, where it's harder to navigate through the sea of cop cars, than it would be to just compete against the racer 1v1. I'm not sure it would be fair for cop cars to be 'ghosted' or 'no-collision' mode, but as a cop your best bet is to strike early if possible, before the slough of cop cars begin piling up, figuratively and literally.
The fragment system for the Cop requires 15 successful 'busts' for a car, which makes sense, as you can potentially end the chases far quicker than a racer can. The % system is the same as above 25/50/75/100 based on whatever event the 'racer' started. Unfortunately this results in a potential issue, where a Cop is now at the mercy of a racer picking the events the cop hasn't already beat. As with the racer crates, once you've received that fragment, you can't get another fragment from the same crate. I think this is a mistake for the police side, because as a cop, you can't select the event you join. You aren't able to start one against the AI either like racers are, so you either repeat the same crate multiple times, or just wait for the room to start a different crate. The former is counter-intuitive, as if I repeat missions as a cop... well then I'm preventing a racer from getting that crate, which will result in them re-starting the same crate, and the cycle continues. It's actually in your best interest to just let them win, and hope they move on to a crate you haven't received. I think Cops should be able to get rewards from repeats, since they have no say in what missions they join into.
Just my .02 after playing for a week