Ubuntu is not a toy. It is, in fact, used widely as a server. At its core it’s as Linux as it gets.

What most people mean by calling it a toy is twofold:

• It is a high level distribution, meaning as a desktop it works pretty much out of the box. This is often frowned upon.
• To some extent, it has diverted from standard Debian configuration. What works on Debian often doesn’t map exactly on Ubuntu.