In sharp contrast with this week's dismal reviews of Windows Mobile 6.5, the Windows 7 client OS received a glowing review from influential tech journalist Walt Mossberg of The Wall Street Journal. Windows 7 has fixed what plagued Vista, and Apple should be afraid, Mossberg writes. The veteran journalist declares that "Microsoft's long operating system nightmare is over" with the arrival of Windows 7, an unsubtle reference to embattled Windows Vista. Mossberg writes that Vista "did a lot to harm both the company\u2019s reputation, and the productivity and blood pressure of its users." Windows 7 Bible: Your Complete Guide to the Next Version of WindowsSlideshow: Windows 7 in Pictures: 10 Cool Desktop FeaturesRemoval of clutter is Windows 7's main appeal, writes Mossberg, as it "banishes Vista's main flaws" such as sluggishness, incompatibility with third-party software and hardware, heavy hardware requirements, and annoying security warnings.Mossberg also touches on what Windows 7, generally available on Oct. 22, will mean for Windows XP, the popular but aging version of the OS that came out in 2001. "While XP works well for many people, it is relatively weak in areas such as security, networking and other features more important today than when XP was designed around 1999 ... With Windows 7, PC users will at last have a strong, modern successor."When testing Windows 7, Mossberg used pre-release versions for nine months and has been testing the RTM version for the past month on 11 different computers, ranging from netbooks to standard laptops to large desktops. On some of these machines, Windows 7 was pre-loaded. Others were upgraded from an earlier version of Windows.Of course Windows 7 is not flawless. Mossberg found drawbacks \u2014 slower than expected startup and reboot times, tedious upgrades from XP-to-Windows 7; a touchpad didn't work after the upgrade \u2014 but still calls Windows 7 "a boost to productivity and a pleasure to use" and heartily recommends it to mainstream consumers.How will Windows 7 affect archrival Apple? Mossberg writes that Apple was given a gift with the problematic Vista, but that free ride is over with Windows 7.In a departure from his usual take on this subject, Mossberg admits: "I, like many other reviewers, have argued that Apple's Mac OS X operating system is much better than Windows. That's no longer true." I think hell just froze over.Mossberg still gives Mac OS X a slight edge for its easier and cheaper upgrade path and for being less of a target for viruses. But he stresses that Windows 7 beats Mac OS in areas like better navigation from the taskbar, easier organization of open windows and touch-screen capabilities."Apple will have to scramble now that the gift of a flawed Vista has been replaced with a reliable, elegant version of Windows."The WSJ review is not the first positive assessment of Windows 7, but it is the first from a international newspaper. Click here to read Harry McCracken's extensive (and mostly positive) review of Windows 7 on PCWorld.com. Shane O'Neill is a senior writer at CIO.com. Follow him on Twitter at twitter.com\/smoneill. Follow everything from CIO.com on Twitter at twitter.com\/CIOonline.