They stick very well, even though our house has textured walls.
We bought the paint from Walmart for $7.99. I didn't even know walmart had their own line of paint, but they do! I read some reviews on it and, admittedly, it doesn't have the highest quality. It is manufactured under the ColorPlace label for Walmart by Sherwin Williams. Most reviews say that if you are willing to do a couple coats it will do just fine for you. We did 2 coats of the "Spring Garden" color.
I think I spent $18 total for the letters & brown paint for their names (and Lauren's initials for her room.)
So all in all, it was a pretty inexpensive way to jazz up the boys' space. We decided to go for it before we moved them together to try and make Ian feel excited about the move. New paint, wall decals, his name on the wall... all ways to show him he wasn't moving into Aaron's Room, but into a completely new room for both of them. Due to illnesses and baby-fussies, it ended up taking us a month to finish the project. I actually think that was really good, though, because it allowed the boys/all of us to get used to the changes gradually. We finished the painting over last weekend. The decals arrived yesterday (& I bought & painted the brown letters yesterday, too) so we pulled it all together before dinner last night with a big, exciting finish! Ian & Aaron helped move Ian's things (bed, dresser, books, etc.) over & it all went great!
They are both over the moon about the new space. For less than $50, I'd say that's a major win.