Hi,
Bombay's are truly fabulous cats, in my experience they are very intelligent and always active. All mine have spontaneously played fetch like a dog and will retrieve objects and bring them to you and drop them in your hand over and over.
They love to get outside, but beware they are quite adventurous and possibly slightly too brave for their own good on occasions. They like to climb and chase and sunbathe.
They don't need any grooming at all and will keep themselves immaculate.
They talk to you a lot but they aren't irritating in the way that siamese can be sometimes, more chatty with a lovely range of chirps, purrs, and brrrrrring sounds.
They need a lot of interaction from you and they love other cats, particularly other bombays and burmese or similar asian cats. My boy was rather territorial, and he did spray even though he was neutered (that doesn't mean they all would) and my girl is a fabulous hunter.
They are truly beautiful animals and have a stunning look, they not just another black cat (much as I love domestic shorthairs also). Their coat feels like silk.
They live to be about 15-16 slightly less on average than a moggy but they don't suffer from any particular breed genetic weaknesses that I'm aware of and they aren;t expensive to insure for a breed cat.
They are heat seeking and will enjoy radiators and all manner of warm places, all mine like to sleep under the bed clothes with you if you'll let them, they also like being under blankets in their cat boxes.
Let me know if you have any other questions I'd be happy to answer them.
Julia.