Ubuntu 9.04 Desktop Edition delivers a range of feature enhancements to improve the user experience. Shorter boot speeds, some as short as 25 seconds, ensure faster access to a full computing environment on most desktop, laptop and netbook models. Enhanced suspend-and-resume features also give users more time between charges along with immediate access after hibernation. Intelligent switching between Wi-Fi and 3G environments has been broadened to support more wireless devices and 3G cards, resulting in a smoother experience for most users.

Which Version should you choose?

Standard personal computer (x86 architecture, Pentium™, Celeron™, Athlon™, Sempron™)
You Should Choose the i386 version.

64bit AMD and Intel computers
You should choose the amd64 version.

The "Alternate" CD does not include the Live CD, instead it uses a text-based installer.