Welcome to ubuntu. Answer is quite straightforward.

There are releases every six months and every couple of years there is
a stable version called LTS [long term support].

You can either update every 6 months if you want to have the latest of
everything or just stick to stable LTS. I find that not enough so i've
decided to update every April.

As you said 8.04 is LTS which gives you stability, but you are not running the
most recent kernel or the most recent versions of programmes. Two years from now
8.04 will still use OpenOffice 2.4, but 9.04 uses OpenOffice 3.0. There are some
programmes worth having the latest release for. This includes the Gimp where 2.6
is so much better than 2.4. Also if you are running KDE instead of Gnome then
9.04 is a must because KDE 4.1 was weak and 4.2.2 is slick. Having the latest is
not necessarily an advantage, however. It depends on your needs and personality.

Also 9.04 allows you to use ext4 which is a new and much faster file system. You
can read ext3 files systems from ext4, but not the other way around.

Upgrading has its risks. Newer kernels sometimes drop drivers for really old
equipment in order to keep the kernel from ballooning in size. If you equipment
is fairly common and only a few years old then this is not an issue. Alos Gnome
and Xorg are new versions as of 8.10 so this means that some things may have
changed there as well.

The upgrade path to 9.04 is to either do a fresh installation or to upgrade to
8.10 which you can do now and then upgrade to 9.04 when it is finalised at the
endo of the month. In other words you cannot upgrade from 8.04 to 9.04.

My motto is stable is for sissies, so I always run the latest and greatest. I do
not mind problems and I test alphas and betas for fun. However, if your system
is working just right and you do not like to install then you need to assess
your motive in upgrading. I will often take a perfectly good system and start
over just for something to do. Call me bent, but it i have it down to an art by
now. Practice makes perfect!

As you said 8.04 is LTS which gives you stability, but you are not running the
most recent kernel or the most recent versions of programmes. Two years from now
8.04 will still use OpenOffice 2.4, but 9.04 uses OpenOffice 3.0. There are some
programmes worth having the latest release for. This includes the Gimp where 2.6
is so much better than 2.4. Also if you are running KDE instead of Gnome then
9.04 is a must because KDE 4.1 was weak and 4.2.2 is slick. Having the latest is
not necessarily an advantage, however. It depends on your needs and personality.

Also 9.04 allows you to use ext4 which is a new and much faster file system. You
can read ext3 files systems from ext4, but not the other way around.

Upgrading has its risks. Newer kernels sometimes drop drivers for really old
equipment in order to keep the kernel from ballooning in size. If you equipment
is fairly common and only a few years old then this is not an issue. Alos Gnome
and Xorg are new versions as of 8.10 so this means that some things may have
changed there as well.

The upgrade path to 9.04 is to either do a fresh installation or to upgrade to
8.10 which you can do now and then upgrade to 9.04 when it is finalised at the
endo of the month. In other words you cannot upgrade from 8.04 to 9.04.

My motto is stable is for sissies, so I always run the latest and greatest. I do
not mind problems and I test alphas and betas for fun. However, if your system
is working just right and you do not like to install then you need to assess
your motive in upgrading. I will often take a perfectly good system and start
over just for something to do. Call me bent, but it i have it down to an art by
now. Practice makes perfect!

Just a rule of thumb. Just wait for a week or two before upgrading. As all ways
there is bugs and most of them are cleared up in a week or so.

Thanks for all who replied. I think I will upgrade to 8.10 now and then to 9.04
when it comes out.