Wow I have 15 channels and I can quickmix it's pretty neat.
15 channels? That's a lot.
I don't like to flip between custom stations or channels more than I have to. I try to get by with 1 per genre. Then I put a lot into making them the best they can be. On Slacker I have over 2500 ratings on my main channel. Pandora doesn't seem to like frequent liking or banning of songs. Seems to cause it to break and loop a small fraction of your favorites.
For several years I was nearly obsessed with custom station/channel services. But I am finding that more and more of these services produce unbalanced custom stations that relate too closely to what you put in. Slacker does the best job in my opinion of making balanced stations, in part due to the vast finetune options. But nearly all the rest, and I have tried nearly every single one, produce stations that grow boring and simply don't feel like radio. Some of them relate to music so closely that they give me a headache after a while. Some of them (statutory licensed) are so bad they seem to ignore the DMCA rules on repetition. Especially when you bring skips into the game.