In a post on this Steam forum thread about a new Serious Sam 3 patch, Croteam's CTO Alen Ladavac has spoken out against Microsoft's latest Windows revision, describing the Metro/tiled UI's Windows Store restrictions as a "horrible" idea, and blasting the certification process currently being used to keep certain mature games off the Store.
After the dreaded 'W' and, er, '8' words were brought up in the thread - specifically in regards to problems a player was having running Serious Sam 3 in Windows 8 - Ladavac responded by expressing his concerns about the service, after apologising for "keeping off topic". His biggest complaint was that "one cannot release a tiled UI application by any other means, but only through Windows Store," referring to the interface-formally-known-as-Metro's disregard for any program/game that doesn't meet their strict requirements. To clarify: Windows 8 itself won't restrict you from installing certain games/programs, they just won't show up in its primary interface.
Ladavac took exception to this, stating that "if it was just about 'being downloaded from Windows store', it would not be a problem. It would be nice to have a common hub to download things from. But to get an app onto that store, it has to be certified by MS. This means bringing the 'console experience' onto your desktop. Each app that you will get through the Windows Store will have to adhere to certain requirements imposed by MS." He went on to shake his fist at the age restrictions that have kept games like Dishonored and Skyrim off the Windows Store, at least in the short term.
Thankfully, that policy has been reversed by Microsoft, although it's worth noting that the Windows 8 app certification requirements still state that any applications "with a rating over PEGI 16, ESRB MATURE, or that contain content that would warrant such a rating, are not allowed." In any case, the games haven't appeared on the store yet.
The suggestion that a hypothetical Windows 9 may block off side-loading entirely (loading programs outside of the tiled UI) is entirely speculative, but much of what Ladavac says chimes with what other outspoken developers, and Valve, have been saying for months now. As PCGamesN explained earlier today, they've been putting their considerable weight behind Linux instead, the beta of which opened just last week.