I don't usually speculate on the intelligence of my cats, although I have a general idea. Intelligence in a feline isn't always a good thing. It's sufficient that they recognize you, remember the locations of their food dish and litter box, and don't roll off the furniture when they're sleeping.
You may not want your cat to be sharp-witted about foreign policy or obsessed with an art-historical period. It can be exhausting if you aren't equally interested yourself, especially if the cat is on a nocturnal schedule and gets lively after midnight. (Possum keeps me entertained with cultural theories during the day, at least.) I once had a cat, Truffalo, who liked to declaim poetry in the middle of the night — always the cat-translation of Hiawatha, which has the same cadences in both languages. (Intelligence doesn't automatically confer taste.) Late-nights with Truffalo were dull yet maddening, in the way of relatives who tell the same stories during every visit.
You especially don't want a cat who keeps trying to hack your computer — believe me, I know. Luckily, Snalbert isn't smart enough to be very successful.
Brainy cats are often intrepid adventurers who get in trouble. They climb, explore, get stuck in tight places, perform experiments — "What will happen if I knock this onto the floor?" — and are always trying new things. We're lucky not to have such a cat; we get more sleep and less breakage.
Smart cats easily figure out how to press your buttons and will eventually train you, without your noticing it, to give them everything they want in exchange for the hope of peace, quiet, and less property damage. When they've done their work well, you won't have the slightest idea that you've been enslaved, you will only think you are a "good cat person." (Could this be you? Unfortunately, you will never have the answer.)
While I prefer my friends and spouse to be smarter than I (and I won't say whether my wish has been entirely fulfilled), I like my cats on the average side, although an occasional flash of genius is fine. I like a cat who chats without giving speeches, plays without setting anything on fire, and won't destroy things for the sake of scientific inquiry.
Wendy is walking around the living room right now, her green snake in her mouth, chirping and "singing" triumphantly. She's adorable. I can't assess the cleverness of what she's doing — is snake-singing incredibly dumb or brilliant? But who cares? She's charming and mysterious. That's all cats need to be.
Wendy can eat kibble and purr at the same time. That has to be an impressive accomplishment in the cat world. I never tire of listening to her. I can't do anything like it. In fact, I still can't make a cup of cocoa without sending a chocolate waterfall down the front of my cabinets. It happened again tonight. My mug is lukewarm and sticky. I am hopeless. Who am I to be writing about intelligence?