Blackwoods is one of only a couple of campgrounds in Acadia National Park, which doesn't allow backpacking. It's connected to the South Ridge Trail, which gives you the opportunity to hike to Cadillac Mountain directly from the campground; we did this for the sunrise on our last day, and HIGHLY recommend it! (See the last picture.)
Rangers consistently patrol the campground, even driving through a couple of times after quiet hours begin; I found this really helped keep the noise down, despite the number of campers. (The campground was sold out for the duration of our stay!)
Each campsite has a fire ring and a picnic table, and sites are spaced decently; I would've appreciated a bit more privacy and space, but I'm sure the tree cover varies based on the site. My friend, who stayed at B121, seemed to have a bit more vegetation between her site and the surrounding sites.
There are plenty of bathrooms throughout the campground, as well as taps with potable water. There is an ampitheatre which is used for nightly activities; I think it can be rented by groups, too. There are showers just outside the campground (8 quarters for 4 minutes; the water isn't always hot, though!) and you can also purchase wood at the shower facility.
One of the routes run by the FREE shuttle bus stops at Blackwoods every hour during the summer; using this shuttle, you can get to Sieur de Monts, Otter Cliff, and the Village Green, where you can connect to any other bus. This is awesome, because it means you don't have to waste half the day jockeying for parking!
Overall, I think Blackwoods Campground is a great value and a great place to camp while visiting Acadia.