I have 3 cats, and trying to adopt one more.
My cats are home while I'm at work,, so they dont' get attention till we get home at night and weekends. They all love each other.
When Angel was the only cat,, she always acted soo sad, and wasn't playful at all... But now that we have Chestnut and Kella, she's alot more playful and acts happier.
There are pros and cons,, the con is the dirtier litter box,, but we have two now to fix that, and my girls ocassionally usually once a week get into a chase inthe middle of the night,, they chase each other, and once we tell them no,, they stop!!
But the more the merrier.. If you get another cat, or kitten get them from a shelter.. There are so many that need homes,, versus buying ones from the store!!!! And I think older cats do better then kittens (less work and you already know there temperment right away,, plus they reallly need the homes)!!!