We've only had Pepper for about 3 weeks now, we rescued him at 5 months old, and Bella (the dane) is almost 10 months old, so we haven't had too much time with them together. The first few days were a handful, but every day since then they're better and better together.
After the initial "slow" getting to know each other, they're fine together and both of them cry and whine if we separate them. Too funny. We worry needlessly about Pepper getting hurt since he's outweighed by over 100 lbs but it doesn't take long to see that Pepper is king of the house and that he takes care of himself just fine. Everyone on this site has told me that the kitties always rule the roost in a cat and dog home!