So far I've mostly used them to make subtle changes in the terrain for gardens and such, and for stairways to heightened entrances.
An example of both combined is my latest build:
https://66.media.tumblr.com/0c96b10488d696e616d6d7f27ab772fc/tumblr_pkt9ngLU6K1v8k7elo10_1280.jpg
The area around the pool is slightly sunken, and the stairs towards the temple are raised.
Another example of stairways:
https://66.media.tumblr.com/6bca9e140d5ea26e441688c5468e4013/tumblr_pjqn9gU6mL1v8k7elo9_1280.jpg
I've been rebuilding Selvadorada, hence all the temple like structures.
And this is an example of smaller, more subtle variations in terrain:
https://66.media.tumblr.com/5fe9e678b13f5328e951e2cd9c69ae9c/tumblr_pi90oiuEcc1v8k7elo3_1280.jpg
https://66.media.tumblr.com/daf85daf68f2814138c13e97c8ccc86e/tumblr_pi90oiuEcc1v8k7elo2_1280.jpg
https://66.media.tumblr.com/8f01fb29e14bdff123f8d5ccbabdbda8/tumblr_pi90oiuEcc1v8k7elo1_1280.jpg
This one's still a WIP, got distracted by other builds.
Obviously, the size of the lot you're building on also is a factor. Small lots don't leave much room for terrain manipulation, whereas on large lots, they can be the perfect way to quickly fill up the lot with unique landscaping.
