Ubuntu fails to showcase many of the best aspects of Linux as a system. Linux (and other open-source OSes, obviously) is an environment in which users are able to exercise more freedom in their usage of their computers than virtually anywhere else. Instead of an environment in which "users" are at the mercy of "developers", the instruction manual is included. Anyone can change their computer's behavior to the extent of their choosing--and there's nobody to tell them not to. Ubuntu takes this and ignores it completely, trying instead to copy user interface features from other projects and environments to win users that like the idea of cheap software.
Not everyone is a kernel hacker, obviously... but Ubuntu should be proud that on Linux every user /can/ become one if they so desire. To emphasize the same read-only one-size-fits-all thinking that Apple has popularized is to disregard entirely the philosophy of the foundation on which Ubuntu exists.
The argument that Ubuntu is a pragmatic, get-things-done distribution is founded in fact; it certainly is. But that doesn't mean it has to make it worse for software development and make it difficult to actually alter your system in meaningful ways. I ran Ubuntu for over a year and every attempt to dig into the system's internals (init scripts, configuration tools, what apt actually /did/, etc.) resulted in frustration because of the great complexity and the lack of any help that the OS itself provided. Comparing distros like Arch Linux that guide their users into the system in order to make the changes they want, Ubuntu is about as read-only as I've ever seen in an open-source Linux-based system.
Even so, Arch isn't a distro for beginners by any stretch of imagination. And there I think Ubuntu has the ability to come out far ahead, if they embrace the fact that they are producing a system designed to be improved by the "end-users". A Linux distribution is not a product like a commercial software package. It's an environment that should foster both productivity and learning. To suggest that users should use a static system or merely accept their updates in 6-month-increments is like suggesting that a carpenter should never consider the manufacture of his tools. Sure, there may be a table to craft today, but improving at the craft of doing so is an important goal--and Ubuntu should help its users improve in their usage of their systems by helping them take small, friendly steps into improving the software they use in real ways.
Stop treating users like children and engage them as equals. Apple can't do that because they have to keep their users dependent. Ubuntu is missing out on its greatest source of potential.