I have two thayeri, and they are wonderful little snakes. They have beautiful colours, they feed enthusiastically, and they have great temperaments. My pair are coming up to about eighteen months old, and feeding on rat pinkies at the moment, or small fuzzy mice - they're tiny.
The only other kingsnake I keep is my MBK, Sabrina. She's about adult corn snake size, and a real sweetie with me, though she has been known to bite men before. I love black snakes, and I like the fact the MBK is a good size for me without being too big, though I'd like a melanistic thayeri in the future so I can have a tiny black kingsnake.
Why no boas or pythons btw? A children's python or spotted python would be a great small pet snake ...