I' m running 10.10 and I would like to upgrade to 11.04 as it hits Beta. Would performance be better with an installation through running the upgrade script or with a fresh install after a format?
In my experience, a fresh install is often better. Most of the packages you've installed either by
synaptic, though the Ubuntu Software Center or by .debs will have been packaged specifically for your previous version, the scripts don't always take account of this, and it occasionally mess up those apps.
I find having a seperate /home partition for keeping your often used files is an excellent solution for not having to reinstall all your data with clean installs.
For more advice on how to do this, go to here.
I tried a couple of times to do an actual upgrade, and always had major issues, which I did not have when I was trying the live version. This was telling me that something went wrong when upgrading. AS a general rule, I now do not upgrade, but rather install the brand new distro. A couple of things to keep in mind:
If you do not want to re-download all your files for the latest DEB packages, that may not be the most recent ones from the ISO, copy all of those form the /var/ directory. There is an actual utility that will backup all the DEB files you had installed, and will restore them. You still have to install them, but tis would save you some download time. This would also apply to applications that are not part of the main distro, but that you want to install. The latest DEB file will likely be readily available to you.
backup your /home directory completely. If it was not at first installed in its own partition, I would recommend doing so in your new install. Later installations can then only point to this directory, saving you time and efforts of file transfer.