Upgrade to Ubuntu Gutsy Gibbon 7.10 from Feisty (7.04)

Step 1
change your repositories:
$ sudo sed -e 's/\sfeisty/ gutsy/g' -i /etc/apt/sources.list

Step 2
open synaptic:
$ sudo synaptic &

Step 3
Click ‘Reload’ button –> Click ‘Mark All Upgrades’ –> Click ‘Apply’

Notes

• This is a shorter method than first upgrading Feisty and then upgrading Feisty to Gutsy as given here: http://www.ubuntu.com/getubuntu/upgrading
  And the three steps mentioned above work (I have tried).
  
• The Gutsy interface is much better. See here: http://www.ubuntu.com/getubuntu/releasenotes/710tour. (latest gnome, gdm, kdm, thunderbird-2, etc. )
• Above procedure can also be tried to upgrade from ubuntu 6.06 (Dapper Drake) to 7.10. For that, step 1 would be:
  $ sudo sed -e 's/\sdapper/ gutsy/g' -i /etc/apt/sources.list

–
HTH
Nitin Munjal