Oh man, I remember running BeOS. It was VERY fast. I then remember skins for Gnome and Litestep that made it look like BeOS showing up shortly thereafter.
I had a few incarnations of it, it is too bad it never really took off, as it had a lot of potential.
It was really the only full effort to bring another mainstream OS(far from that goal but it had potential). The problem with Linux is that there is no real "standard". Yes they finally did away with multi-CD installations and put it into one CD ala Ubuntu, LinuxMint etc but so far from 100% casual use. Part of the issue lies with manufacturers refusing to provide source for drivers.
I ran on Ubuntu 8.04 for nearly a year trouble free Windows free except for my Zune. Installed VirtualBox with Windows XP and it worked flawlessly for synching my zune. The information is out there and makes linux very easy to work with if you understand PC's on a slightly deeper level(terminal etc). BeOS just worked for the most part but didn't have the support needed to make it flower.
OS/2 Warp was a quick bugger. To bad we get nothing cool like that anymore. I despise Vista, Windows 7 wasn't bad when i was testing the beta, but some nuances I didn't like. Dragging and dropping in folders can be a chore, and the stupid Virtual Documents folders to this day are horrible.
Actually decided to go back to linux again, downloaded Linux Mint(Gloria) v7. Like its aesthetics and its core is Ubuntu/Debian.
I've been using Linux as my sole operating system since Microsoft released the vista fiasco. I've used Linux at work since 1997 and love it. But no matter how experienced you are it does take a lot of tweaking.
I would prefer an off the shelf OS that just worked. OS X seems to be close, especially with BSD underneath. The price points for the more powerful Apple machines is what stops me from getting a Mac.
People rag on Win95 (and OS/2 Warp, too, for that matter). But there's something you have to remember:
Those were multitasking OS's that ran (and ran well) on a 486 with 8 MB of RAM and 125 MB hard drive (and you could even install them from 3.5" floppies).