One of the most exciting changes in Ubuntu 9.04 is improved support for a number of netbooks, particularly models with Intel Atom processors.
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Long story short, when I plugged the Ubuntu 9.04 flash drive into my Eee PC 1000HE, the operating system booted quickly and all of the hardware just worked. The keyboard shortcuts for adjusting the volume and screen brightness work, the WiFi card is recognized, and I connected to my home network in a matter of seconds. The only problem I noticed is that the speakers seem substantially quieter than they are under Windows XP or Windows 7.