1. Windows 8
1.1. Pros
1.1.1. Windows 8 sports a radical new look and feel that was once called “Metro” Windows 8 sports a radical new look and feel that was once called “Metro”
1.1.2. Windows 8 was designed from the ground up to provide a snappier operating system that takes advantage of the latest advancements in hardware and processing tools
1.2. Cons
1.2.1. Windows 8 makes the process of connecting to Active Directory a little more difficult from AMD chip based devices
1.2.2. Windows 8 does away with the traditional task bar and features a completely new ribbon-based interface for first-party applications.
2. Mac OS X
2.1. Pros
2.1.1. Modestly improved performance compared to "Leopard" on Intel-based Macs.
2.1.2. For "Leopard" users, very inexpensive compared to most operating system upgrades.
2.2. Cons
2.2.1. Does not support PowerPC Macs, even those sold barely over three years ago, providing significantly less support than typical.
2.2.2. Some existing MacOS X software and peripherals are not compatible.
3. Ubuntu 12.10
3.1. Pros
3.1.1. Popular desktop Linux distribution based on Debian, with a fine pedigree
3.1.2. Easy to install
3.2. Cons
3.2.1. Ubuntu's controversial desktop shell, Unity, has still to mature
3.2.2. Recent trends towards 'commercialisation' (the addition of online shopping 'suggestions' to the Dash search results) have annoyed some users