This isn't an Ubuntu bashing post. I really like Ubuntu and have been using it since it was first released back with Warty in 2004 and as my only desktop OS since Dapper back in 2006. It is just with with all the bits that have been added over time my machine is feeling really slow.
In fact I log in and wander off for five minutes to give it time for the Update Manager to have a think, UbuntuOne to do whatever resource munching insanity it likes to do and all the other mostly pointless services to get themselves sorted out before I can start work.
I can barely remember the other OS but this recent slowness has that old smell about it.
It was suprising to see quite how much is started by default. So I figured I'd go through and disable or remove each of these services that I don't want.
The easiest way to do this is to edit each file in /etc/xdg/autostart and change the line NoDisplay=true to NoDisplay=false. You can use sed to do this in one line
sudo sed -i "s;NoDisplay=true;NoDisplay=false;g" /etc/xdg/autostart/*
This stops these services being hidden in the "Startup Applications" settings. Then open the Startup Applications settings and untick the services you don't need.
The list of things that were doing nothing more than wasting resources on my PC were: Backup Monitor, Bluetooth Manager, Chat, Check for new hardware drivers, Desktop sharing, Disk Notifications, Evolution Alarm Notify, Gwibber, Onboard, Orca Screen Reader, Screensaver, Ubuntu One, Update Notifier and User folders update.
All of that was running in the background on my PC thanks to decisions made by Ubuntu and they even took the time to hide the ability to turn this off.
Also bear in mind that if you have other user accounts on your PC and they are logged in, they may also have pointless processes running. You will have to untick the Startup Applications on their log in too.