From memory O_O
Fo3 had some high level creatures from the start of the game, as opposed to Ob levelling everything (?). If I remember correctly the Fo3 method of levelling most creatures and NPCs was almost identical to Ob, you see this when the species in a certain area change over night, what you don't see is the sudden glass armor syndrome from Ob. Beth got a bit clever here, instead of giving, say, raiders better weapons and armor as their level increased (glass armor syndrome) Beth started the raiders with gear in poor condition and it was the condition of the gear that improved with level. Smart, no glass armor but the overall idea of trying to maintain a constant level challenge remained the same.
This last bit is an important point as I suspect Skyrim will attempt exactly the same thing but with one interesting difference. The GI article mentions that increasing the level of skills that are already at a higher level will level your character more quickly than increasing the level of skills currently at a low level... Still with me? lol. So, if you charge through the game with a 1 handed sword you will level relatively quickly and your sword skill should be a match for the levelling mobs. If on the other hand you do a bit of sword play and a bit of magic and a bit of alchemy etc then your character will level more slowly than the sword specialist and hopefully, and unlike with Ob, your more diverse skills will still be a match for the mobs levelled to match your character.
Err, I think.
Edit:
Oh yes, we want hand placed loot and non-levelled special items and at least some fixed level encounters.
Edit2:
It was milder than in Oblivion and NPCs had leveled weapons, but they didn't have leveled armor.
I'll accept that, the trick was just on the armor then