OK, so I'm 3/4 of the way through the build now. A few comments:
I'm not a fan of the way the levels of this modular stack together. Instead of having the plates on the underside of the floor that lock in the next level, these rely on 3-4 studs around the edges of the bottom floor. It uses the same method the smaller creator sets do, but doesn't feel right.
The bottom front floor of the Pet Shop building is a lot like the Green Grocer first floor. A LOT. This may make it blend in seamlessly next to the GG, but as far as variety goes, there is little. The inside isn't as populated as I thought it would be either: a dog, a cat, an aquarium, a shelf and a register are about all there are.
The positives though: The Pet shop staircase is hinged on some technic pins, so you can move it out of the way to get to the dog pen. The colors are really nice, the Maersk blue gives some nice variety to the buildings. The townhouse has a lot of cool features: bathroom, phone, trap door, spiral staircase, rooftop garden. I really like the railings on the front door too. There is a lot of reddish brown though, and the roof itself is kind of plain: just a few tiles and a chimney (where's the fireplace?).
Overall, as a few others have said, it would have been awesome if this were two separate sets. I don't feel like I'm building something really big, and a lot of build is just building up walls with normal bricks. Still, an above average modular building would be an outstanding normal City set.