Kurseong is a cute town. However, there aren't many options when it comes to things to do. It's perfect as a place to stop at for those looking for somewhere extremely peaceful after a hectic slog through India. It's also a reasonable option for those who want to avoid the crowds in the famous town of Darjeeling. However, it offers too little of interest to justify a stay of several days.
You can go for nice walks, visit tea plantations and climb aboard the famous train. If you're a tea professional, you can take a course. I should also point out that there are some nice, isolated lodges for romantic couples to stay at. Apart from that, there isn't much to say about the place.
Kurseong is one of the places the steam-driven Toy Train stops at on its way from Darjeeling. It's therefore one of the essential places to visit if you are visiting India as a family. You'll also find it a more relaxed, easy going place to stay than Darjeeling. Having already travelled on the little railway of Ooty up in the mountains of Kerala, I didn't see the point of repeating the experience with the one here.
What I can recommend, however, is a stay at one of Kurseong's tea estates, which will give you the opportunity to join in the harvesting process with the tea pickers, learn about how tea is made, and, of course, sample and purchase genuine tea of the "made in India" kind. Even though, and in contrast to some tourists, I really enjoyed my visit to the Happy Valley Tea Estate in Darjeeling, I have to admit that the fact you get to have such close contact with the workers made Makaibari an even more interesting place to visit. Fans of responsible tourism should especially enjoy it!