Thanks. I actually read the label on my bottle of Murphy Oil Soap and it said I could use it on painted surfaces.
So, just to be sure, I called the company (toll-free number was on the label) and asked them and they said as long as I followed the instructions, it should be fine. That's 1/2 cup to a gallon of water.
If I don't like the way this works, I will go buy the 409 but I happened to have the Murphy's on hand.
You have to be careful with the magic eraser--it does take off paint. Depending on how hard you scrub and what color your paint is it might not be noticeable--initially it'll just take the gloss off of paint and make it more matte, but eventually it will take the paint off. But sometimes it's the only thing that'll get the dirt off too, so you just need to be careful with it. If you have light colored paint it's generally not super noticeable as long as you're not having to clean the same spot over and over again.
We just washed our painted walls and ceiling in the kitchen using TSP. It didn't hurt the paint. The ceiling in the kitchen yellowed from years of cooking. TSP cut through it all and the ceiling looks good as new.
TSP is trisodium phosphate--it's a cleaner that people frequently use to clean surfaces prior to painting and things like that--it really gets all the dirt off. You'll probably have to go to a home center/hardware store to buy it though, you won't find it at the grocery store.
Woodspirit1: It will do a good job cleaning your ceiling and walls whether it's from cooking or nicotine stains. I've never tried it on a glossy painted surface, don't know if it will dull the shine or not. I used it yesterday on the metal, back door, and on the refrigerator and stove. You can find TSP at paint stores, Ace Hardware, etc.