Hit and miss staircases, as they are amusingly known, can seem a scary prospect, especially when you are looking down them! Get the wrong foot first, and getting to your loft will feel a little like climbing Everest, get it right, and you will find it a surprisingly pleasant experience.
There is a story about alternating tread staircases being called “Witches staircases”, the idea being that witches can't climb up them, presumably their feet are too big? In New England and around Salem the tale goes that there are lots of hit and miss stairs, and that these are to provide safe spaces for the inhabitants where the witches can't go! Turns out that this story did not start in Salem in the 1690's, but on Twitter in the 2020's, fun though.
A space saver staircase or alternating tread staircases can take up about half of the space of a conventional staircase, making them very tempting where your space is a premium. You may even find that it tips the balance of whether a loft conversion is practical or not. They can be used to access a single room, or single room with a bathroom. Essentially these are for a person who regularly use them, not for main staircases in your house.
As a design challenge I really like alternating treads. They throw up lots of interesting geometry, and so can produce sculptural shapes. They are suited to incorporating into storage or furniture. Not only do they take up less space than a traditional staircase, but that space can be combined with bookshelves or storage. A well designed space saver staircase can be a feature, not a compromise.
Check out my staircases page for ideas!