Opera Software A/S will commercially launch the latest iteration of its Windows browser, Opera 4.0, at PC Expo on Tuesday. Opera's main claim to fame has been its small download size, speed and ability to be customised. Besides running on Windows, Opera is available in a wide variety of flavors for platforms including the Macintosh, BeOS, Linux and EPOC. Opera also is one of the few remaining Windows browsers that isn't free. Version 4.0 will cost $39 (£26), and will be available for download from the company's Web site or via its ISP and other partners. The 32-bit version will run on Windows 95, 98, NT 4.0 and Windows 2000. Opera 4.0 for Windows has been in beta since March. Opera Software is claiming the product is "the fastest browser on Earth." Features that Kjeller, Norway-based Opera Software is touting as part of its latest release include integrated email; fast rendering speed; low resource requirements; 128-bit encryption; XML; cascading style sheet; HTML; ECMAScript; and JavaScript support. Opera's unveiling comes on the heels of Microsoft's announcement last week of its next-generation "new user experience" directions. Microsoft unveiled for press and analysts its Microsoft.Net roadmap, with hardly a mention of the word "browser." Instead, the company talked up its future Microsoft. Net user experience, a presentation layer that rides on top of a set of rendering engines, to which Microsoft is referring as a "universal canvas." Microsoft .Net User Experience 1.0 isn't slated until 2001, when Microsoft makes the new interface available as an integrated part of its next-generation Windows client, code-named Whistler. Microsoft isn't the only company that has made browsers free commodities. America Online's Netscape division continues to labor on the next-generation Netscape browser, Version 6 -- or, as it is more fondly known, Mozilla. Last week, the mozilla.org open source development team released to testers Milestone 16 of Mozilla. The final commercial version of Mozilla is expected before the end of this calendar year. And newer browser competitors, such as Ithaca, N.Y.-based Sutton Designs Inc., are breathing down Opera Software's neck, as well. Sutton Designs markets a browser called Enigma for Windows 95/98, which the company claims is fast, lean and "free, unlike Opera." What do you think? Tell the Mailroom. And read what others have said.