For reference, we stayed in spot B44 during mid January. It's an excellent RV pull through site with 30amp electric service and the Virgin River going by just 20 feet away. I'm actually writing this while we're still here, we leave tomorrow, checkout time is 11am. It's a nice campground and there's a good chance you'll see some wildlife. We woke up this morning to 5 deer grazing on some grass right across the river and then later we hiked the Watchman Trail, which took us 2 hours roundtrip, and saw 7 Bighorn Sheep.
The campground has clean restrooms and there are dumpsters for trash within a short walk of most sites. Our site is directly across from a restroom and dumpster. And no, there is no odor from either. They're far enough away and well maintained.
The visitor center is a short walk from our site, I would guess around 1/4 mile or so. They have tons of souvenirs and an information desk.
There are also several popular hikes that start within the campground, get a park map when you first enter Zion Park. It will show where the hikes are located and what difficulty level they are.
I highly recommend staying here.