A common theme in your posts is a big environment with lots of variation - easier said than done of course <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" /> If you'd have to chose between:
Lots of levels with each level being very different, connected through a map a.k.a. Baldur's Gate or Fallout
One big seamless world with more or less similar graphics throughout the map a.k.a. Oblivion
Less detailed graphics in one big seamless world but with lots of variation a.k.a. World of Warcraft
to answer Lar's question, i would pick option 1, then 3. i don't think i will like 2 as i really hate Oblivion (for being first person perspective).
probably to be more realistic, i would like to have a mix of option 1 & 3, as i prefer for the world not to be cut up according to level, act or story arc. probably the region can be cut up this way (like Fallout).
almost seamless is good as seamless often means toning down the graphics (otherwise rendering will be too much for older systems).
i like Draggy's idea about setting up the atmosphere which can use the same tile set but with different set of behaviour. it does give a lot of visual clue which require no words to convey.
what elgi said is something i agree too. however with the world cut up into different maps & areas, the current set of world can be easily expanded via teleporter stones or portals. thus the freedom is still there without ruining the balance of the original set or map.
Tutamun has a lot of great ideas. i quite like the part about travelling time which the journey can take from a day to months, depending on the distance. i would like for that idea to be expanded a bit with players being able to see their characters taking the route (drawn on the map of course) & with the ability to stop at anytime along the route.
i guess this may mean some kind of cookie cutter side quests (a bit like BD Battlefields) so those who like to do lots of side quests, no matter how boring they are (people like me <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" /> ), might like this.
my 2 cents. <img src="/ubbthreads/images/graemlins/delight.gif" alt="" />