I use the Theban alphabet in my ordinary day-to-day diary and also in my "spiritual, magickal journey" diary. It's not a proper BoS, but more of a journal of experiences. I bought this lovely journal book and copied everything I had into it using Theban. It was well worth it, the letters are extremely beautiful.
I have been using the alphabet for more than a year now, and I found it's easier to learn to write it than it is to actually read what you have written, or at least that was the way it was for me. I use long spaces to separate words so it's easier to read. I'm thinking about making my own alphabet to further conceal my writings, and also because I would want to make each letter beautiful and easy to write by hand. I've looked at some letters from movies and tv-shows to find inspiration, like Lord of the Rings, Buffy the Vampire Slayer, The Shannara Chronicals and a few others. Using another alphabet makes each page stand out in beauty, hides what you have written, and gives each word it's own power and mystique. You can use this alphabet no matter what language you use, I created extra letters for the Norwegian alphabet which has 3 extra letters compared to the English alphabet and I write in Norwegian using Theban.
I like the look of Theban, and I like that people can't just open my diaries and read what they find. As I used the alphabet, over time some of the letters changed a bit, into my own handwriting, which I didn't expect to happen, it just did. I know I will keep using it until I make my own letters.