I installed Longhorn+Whidbey+Longhorn SDK on a PIII/800MHz/292MB/10GB HDD system. I am left with just less than a Gig of HD. I am using this for the past 19 days. I am left with less than a Gig HD space after installing all of these. System gets crashed frequently as expected (less RAM and less HD Space). But I like the side bar feature. I wrote a small Sidebar application, which pulls information from various sites and scrolls the information. My laptop ethernet card was not recognized somehow (I think PCMCIA has issues with Longhorn), so I am using the modem connection. WinFX (code name for .NET Framework and Unmanged API, which is part of Longhorn SDK). I liked Avalon and Indigo parts of WinFX. I havenot fully worked on WinFS though. I haven't tried Yukon yet, because Yukon is not supported on Longhorn. More to follow here.