Mac OS X 10.9 Mavericks
As it's a free upgrade that gives you more apps, improved features across the board, and better performance, there is really no reason not to get Mavericks on your Mac.
Microsoft Windows 8.1
If you're a dedicated Windows 8 hater, the update to Windows 8.1 isn't going to change your mind. For everyone else, this collection of tweaks, fixes, and new features is useful, but everything here should have shipped in the original version last year.
Microsoft Windows 8 Pro ( Upgrade)
Microsoft makes an aggressive, forward-thinking, and bold statement for the future of PCs with Windows 8, and vast security and speed improvements more than justify the $40 upgrade price.
Apple Mac OS X 10.6.3 Snow Leopard
Intel Mac users will like Snow Leopard's smartly designed interface enhancements, and its Exchange support is a must-have (especially with Outlook for Mac on the way). With a ton of technological improvements, Snow Leopard is worth the $29 upgrade fee.
Microsoft Windows 7 Home Premium
Windows 7 is more than what Vista should have been, it's where Microsoft needed to go. How much damage Vista did and whether Windows 7 is enough for people to finally abandon Windows XP are questions that nobody has the answers to right now.
Mac OS X 10.5 Leopard
The grace of Leopard's interface enhancements makes productivity more pleasurable with a Mac, as more than 300 functional and fun features top off this update.
Apple Mac OS X 10.4 Tiger ( Family Pack)
Though its new user features have mixed appeal, Tiger's technological changes and speed improvements make this an enticing upgrade, especially for those who passed on Panther.
Windows Vista Home Basic
Windows Vista Home Basic is essentially warmed-over Windows XP, Windows XP SP3. If you're currently happy with Windows XP SP2, we see no compelling reason to upgrade. On the other hand, if you need a new computer right now, Windows Vista is stable enough for everyday use.
Windows Vista Business
Windows Vista Business is essentially warmed-over Windows XP. If you're currently happy with Windows XP SP2, we see no compelling reason to upgrade. On the other hand, if you need a new computer right now, Windows Vista is stable enough for everyday use.
Microsoft Windows XP Home Edition w/SP2
We recommend installing Windows XP SP2 but only after Microsoft has had a few weeks to work out the kinks.