Tech giants like Apple have been quick to plug HTML5 as the web language of the future — and consequently, a “Flash killer”– but when it comes to features and how those will affect mainstream users, there’s been little in the way of clear explanation.

Authored by Google employee Ian Hickson, HTML5 promises to be the “genes” from which all web sites will eventually spawn. Unlike web specs that came before it though, HTML5 in its full maturity should offer much more than just plug-in-free, buttery-smooth video and audio playback.

Eventually, users of mobile Apple devices won’t have to launch dedicated iPad or iPhone apps from say, ABC, just to watch their favorite shows — they’ll watch inside their browsers instead. Other perks? Geolocation, a feature popularized by apps like Foursquare that lets a service ID your location if you want it to; dragging-and-dropping of items from the desktop to the browser (and vice versa); faster web site loading using the computer’s graphics chip; and use of in-browser apps offline — a major boon for casual gamers.

When ever HTML5’s tools are ready and they achieve widespread adoption — Hickson gives an extremely conservative estimate of 2022, while Google stated last week that it expects most browsers to be fully HTML5-ready by end of the year — then fully expect a highly-evolved web browsing experience.

Still, some major companies remain reluctant to jump on the bandwagon. Here’s where they stand:

Apple: If you haven’t kept up with the company’s intensifying public feud with Adobe, here’s a quick refresher: Apple has never allowed Flash to run on any all of its mobile devices, attributing the decision to the plug-in’s sub-par performance. And last month, Steve Jobs made his opinions crystal-clear with a 1,600-word missive dubbing HTML5 “the future” and Flash a buggy, battery-sucking relic of the past. In other words, don’t expect to watch any Flash-based video on your Apple devices, well, ever.

Microsoft: In a twist, Redmond comes down on Apple’s side of the war. Dean Hachamovitch, general manager of Internet Explorer, recently echoed Jobs’ sentiment about Flash in a blog post and discussed plans for the update to its popular browser, Internet Explorer 9, to support HTML5.

Google: Though Android 2.2, codenamed “Froyo,” introduces Flash support, the company has been pretty up-front about its affinity for HTML5. YouTube, which Google acquired in 2006, hosts an experimental site where users can run videos in native HTML5. The catch: not all clips are watchable, and the test site doesn’t run on all browsers. And for those wondering about VP8, the open-source video format unveiled last week at Google’s developer conference, it will play nice with HTML5 thanks to Google’s free licensing.

Netflix: When Netflix cloud architect Adrian Cockcroft blogged that Netflix would begin to incorporate some HTML5 in the company’s codebase, some took that to mean that HTML5-coded movies were on the horizon. (Currently, Netflix uses Microsoft’s Silverlight plug-in.) Later, he penned an update stating that wouldn’t be the case, as the web code lacks a digital rights management (DRM) solution that would protect studio films and TV programs from piracy.

Hulu: Same deal as Netflix. VP of product Eugene Wei went on the record via Hulu’s blog stating that HTML5 “doesn’t yet meet all of our customers’ needs.” In other words, it lacks a DRM-like solution, and the tools needed to handle data reporting for advertisers, high-quality video rendering (at least as far as Hulu’s concerned), and communication for server buffering. So until HTML5 appeases Hulu, or Hulu finds a workaround and relaxes its standards, HTML5 hopefuls are plumb out of luck.

CBS: Eager to capitalize on the iPad’s early success, the network plans to update its site from Flash to HTML5 in time for the fall 2010 TV season. Currently, full episodes of the show Survivor, as well as select clips from other shows, are available in the format.