From what I understand, it had a lot of bugs and glitches that made its overall operation undesirable, and that is was also rather slow and laggy at times and ate up a lot of RAM, diskspace, and battery life (on laptops, that is). I've also heard that since it was the first Windows OS that was made specificaly for wider monitors like 16:9 or even 16:10 that it couldn't properly adjust to 4:3 screen resolutions like a 1024x768 or 1152x864 (instead stretching the display out rather than pillar boxing it). Apparently, it was also not a very good OS for multimedia like videos and gaming and such.