Since I like to live life on the bleeding edge, I upgraded not one but twice on the day Ubuntu 8.04 (Hardy Heron) was released. And there's not much to say really. The whole experience was painless. The process of upgrading from 7.10 was a bit slow on an aging Toshiba laptop, but that was due to the processor (1 GHz Celeron) and limited RAM (750 Mb). Performance knocks the socks off Windoze XP which had essentially become unusable on this machine. A new installation on a shiny Mac Pro (via Parallels) was much faster and equally effortless. And that's all there is to say.
Except, as Steve Jobs would say, one more thing.
There's a problem. Installing new software on any version of Linux, Ubuntu included, is still painful, and beyond the ability of mere mortals. Whether you use the Synaptic package manager, terminal, or whatever, even if there is a Debian distro of your favourite gizmo, Joe Public can't install new software. Unless and until Linux moves to a click-on-a-link, oh-here's-an-installer, click-the-Agree-button model of software distribution in some way similar to Windoze or OS X, it's not ready for prime time and it won't be able to rule the world. I wish I didn't have to say this, but it's time for Linux (and I think we're talking Ubuntu here), now in it's difficult teenage years, to grow up and face the facts. In the real world, the geeks are not always going to be there to hold its hand. It has to be able to stand on its own two feet.
Update: Liam's suggestion