In a word, Leopard is amazing and makes the Mac even more fun to use. And probably more productive too, but I guess that comes after you have fun with it. But there is one small issue to do with x11 not working properly. A bit of googling brings up this post:
http://discussions.apple.com/thread.jspa?messageID=5666206
But the relevant info is here, about 10k words down the page 
I reinstall X11 form the original leopard image. All the package X11User.pkg (hidden in /Volumes/Mac OS X Install DVD/System/Installation/Packages), X11Documentation.pkg and X11SDK.pkg from /Volumes/Mac OS X Install DVD/Optional Installs/Xcode Tools/Packages.
November 7th, 2007 at 9:17 pm
I now get the following when logging into shell, very strange.
andrew@andrew-johnstones-computer ~$ bb
Warning: No xauth data; using fake authentication data for X11 forwarding.
root@bullbearings.co.uk ~
November 26th, 2007 at 9:50 am
I added these lines (from a linux box) to the /etc/ssh_config file and now X11 ssh works on Leopard
Host *
GSSAPIAuthentication yes
# If this option is set to yes then remote X11 clients will have full access
# to the original X11 display. As virtually no X11 client supports the untrusted
# mode correctly we set this to yes.
ForwardX11Trusted yes
# Send locale-related environment variables
SendEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
SendEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
SendEnv LC_IDENTIFICATION LC_ALL
February 11th, 2008 at 11:11 am
I installed X11 2.1.3 release, which is fairly updated, there are few changes in lib also fixed ‘login_shell’ defaults key usage when launching from the Applications menu.