I spent the first few months as a DSLR user thinking I had a grasp of what the 18-55 can do. But after a few months I started trying to educate myself about managing DoF properly, minimizing camera shake, lens “sweet spots”, etc. and I couldn’t believe how much happier I started to become with my results. There were a few photo outings that were nothing short of a revelation for me—those sweet “aha!” moments. It’s not that the photos were terribly memorable or interesting, but that’s not always the point—sometimes you just go out and shoot to see what you can learn; capturing a keeper is just a bonus.
I’ve always said that I refuse to even consider upgrading until I feel like the lens is “getting in my way” at least semi-regularly, but so far I’m just not seeing it.
As for the OP’s comments about the 55-250, I have that one too, and I’m not sure what he’s on about, comparing it to the 18-55. There may be some minor overlap in their use cases, but for the most part, I find them to be almost mutually exclusive tools.