As far as my amusement park travels go, I've hit all the major cities and the large parks that go with them. Sure, there are dozens of parks left around the country, but they are all very small or pretty far out of the way. It's getting more and more challenging to fit them in!
Getting pictures of the third coaster, Super Coaster, is very difficult from the ground. It's not exactly hidden, but the positioning of surrounding rides and trees make for very unflattering photographs. It was a bit faster than Discovery, as it had an actual drop. Super Coaster is smaller, though. By the time I finished riding the other coasters, it still had a large line.
The plan had been to ride the three coasters, take some pictures, and get out. The long line at the entrance and the long line on Super Coaster delayed me enough that I missed my planned train. The next one was an hour later, which coupled with the delay allowed me time to get on the Ferris wheel and browse the gift shop.
The bus stop is right outside of the park. Buying the free pass plus round trip bus ticket (from Yamagata) set costs the same as a free pass, essentially making the bus trip free. Note that the bus runs about once every two hours, and takes 20 minutes from Yamagata Station.
Admission to the park is cheap but a full day of rides adds up fast; adult free passes are 3800 yen, but admission only is 800 yen. Lina World has lots of dining options at the park, and there are hot springs near by so it is possible to spend a full day in the area. It's open from mid-March through mid-November, with varied hours depending on the season (opening between 8:00 and 10:00, closing between 16:00 and 19:30).