Nah, no turn based fighting, no linear gameplay

At the beginning you design your character, from his race and appearance to his individual strengths, and abilities. Magic, stealth, fighting, or a mix or any, it's up to you. It defines the way you face combat in the game, more on that in a sec. What then happens is you are placed in a 16x16 square mile map, and pointed in the direction of the main quest. You don't need to do that, ever if you don't want to. There are hundreds of side quest all acrossed the land as well as, caves, ruins, town, villages, camps, etc, with people, monsters, bandits, quests all in between. Fighting takes place either 1st or 3rd person, depending on preference, though most people will agree 1st person is the way to go. Depending on how you designed your character, you will fight differently. Magic; fireballs, lightning blasts, charming people to fight beside you, summoning monsters as well. Stealth; daggers, bows, hiding, stealing, extra damage on unaware strikes, etc. Combat; bash their heads in with longswords, claymores, axes, hammers, clubs whatever. You could also shield up... if you want.
Ok I admit my writing skills are sorely lacking. Watch this Oblivion GT review instead.
http://www.gametrailers.com/player/9920.html