John B.
Yelp
It's quite a pleasant site, but compared to other local attractions, Magnolia didn't blow me away. The price is quite high and is on a per-person basis and includes additional charges for a variety of activities, but the Charleston tourism scene clearly doesn't lack for customers so it is almost always busy. The signage promises the gardens have a relatively natural feel, which is true, but for me, I found some of the more manicured spaces up the road at Middleton to be more beautiful and interesting.
Conversely, if you're interested in history, some of the other plantation tours give you history and don't charge you extra (McLeod, for example, which is closer to the city), whereas here the admission fee pretty much just lets you walk around the grounds and does not get you inside the house or to the boat that roams the swamp or to the slavery lecture.
There is a nice swampy section by the river, and you can see a variety of birds and likely some alligators, but again, in comparison to other spots, notably some parks on the coast, this is not the best wildlife sighting area (Bull Island is probably the best for that).
If you had a really short time in Charleston and really wanted to cram a bunch of stuff in and didn't mind spending the money, Magnolia is a nice place, but I've definitely found other spots that I like better.