I like them too. They tend to stay way more upright and uniformly lush, an Astilbe never gets woody so the bush doesnt crack and fall over leaving gaps like lavender can.
Take a minute to think what it is about them you like.. is it the way they maintain their shape, Astilbe is very organized, vertical and predictable. Is it the flower shape, is it the color, is it the time of year it blooms?
Here's another question. How do you pronounce it?
ASTibile, ah-STIB-Lee or other?