Earlier this year, Samsung Italy announced that the Samsung Omnia W would receive Wi-Fi tethering capability with the Windows Phone 7.8 update. Well... that didn't happen.
Samsung Italy sites that the Windows Phone 7.8 update was issued directly from Microsoft and for whatever reason, the tethering feature didn't make the cut. That's the bad news. The good news is that Samsung Italy is working on a separate maintenance update for the Omnia W that will bring tethering into the fold. Look for the update to hit the air in the coming weeks.
Source: Windows Phone Italy