One of the most notable difference is represented by the fonts. They look now much prettier than before. Below is an example:
The Ubuntu Software Center has also been changed, bringing you new features, such as "What's new", "Where is it", the ability of handling .deb files or paid applications. Actually, there's only one paid application now, but it is just for testing purposes, more are expected to come with Ubuntu 11.04.
The installation process has been completely redesigned. Andrew (from webupd8) shot a video of it:
Ouch, I was about to forget about it. There's also a new wallpaper into Ubuntu 10.10 by default. The old one, which has been a little redesigned compared to the one present in 10.04, created a real scandal and was changed after some users reported even a bug into it. So, it now looks something like this:
Other changes are represented only by under the hood improvements and updates to most applications, changes that are seen rarely or aren't at all for the end user.
Ubuntu is available for download from here.