Always do a fresh install. Try to create separate root and home folder. This
will make it easier for you to keep your data.

Ubuntu 10.10 is in early alpha and is not meant for every day use. The 10.10
means that it comes out in October of 2010, still 4 months away. It is buggy
because they have not worked out the bugs yet. Alphas and Betas are meant
for users who wish to test it out and report bugs so that they can be
squashed.

Your best bet is to re-install Ubuntu 10.04 and stick with it until 10.10 is
ready for everyday use. Even then only people who want to upgrade should.
There is three years of support for 10.04 and only 18 months for 10.10.

I prefer the fresh install myself, and with the home partition separated
out it's fairly painless. Upgrade is for quick and dirty only.

But look, if you've gone up to 10.10 then it's still in its first Alpha
isn't it? Certainly a long way from release. There's large disclaimers
on the download page about how it's not finished, and not to use it on
production machines. Give it a fair crack, wait till it's officially
available before criticising it

I have never done an upgrade,but I have
heard of complications resulting from this.

10.10 is not under my area of expertise, ether,though.
Might want to reinstall if it isn't a big hassle.

The 10.10 alpha is meant for those who enjoy testing and bug hunting.

The question arises, how can you switch from a long term support version
of ubuntu to an experimental test version and not expect problems? 10.10
is not even beta yet, and is *not* recommended for new users, casual
users or production systems. Lots of breakage is expected between now
and the time it gets to -RC status.

I went from 9.10 to 10.04 because I kept
getting prompted, but I waited for a while, then figured that maybe the
bugs had been worked out since April. I don't have 10.10 yet, but from
now on, I'm not going the upgrade route. I will do a fresh install -
too many problems...

I always do a fresh installation as it produces a
satisfactory experience every time. Of course, I have a separate /home
partition which makes installation easy and I can install in my sleep and
frequently do, I think.

I totally echo this opinion. I just did a triple boot system with Windows XP
Pro, AV Linux and Ubuntu Studio 10.04 and even though I haven't had time to
really dig in, so far I'm really pleased with the newest version of US. Now
if I can install KDEnlive without botching Ubuntu I'll be really happy!

You do not need to do a fresh install of every desktop.
http://psychocats.net/ubuntu/kde

I should clarify that in my case, fresh install was the only option as it's
a new system all around.

This has me scratching my head. The article does not address fresh
installation vs. upgrading at all. It is about adding an additional desktop
environment, in this case KDE as well as GNOME.

Depending how old your system is or how much ram is in. I done upgrades on my
celeron with 1 gig of ram just fine. I do admit it may be time for a system
upgrade soon. You may want to bump up the ram.