The main arguments of the level-scaling proponents seem to be that in a non-linear game one could get too powerful for the main quest, or that the main quest is too challenging if one sets out on it without any sidetracking.
However, I disagree with the necessity of level-scaling based on those arguments, especially in the case of the latter one. In my opinion someone should have to explore, grow, and fulfill arbitrary tasks before he can set out on his/her path of glory (main quest), and to me this is one of the appealing aspects of a non-linear world. This might not be a popular view in this age of casual gaming, but it's my personal preference. No pain, no gain. I actually feel cheated if my choices, training and grinding do not pay off.
If you get that feeling, then clearly the game designers have failed: they've been too obvious and too heavy-handed about the level-scaling. Too much salt will ruin an otherwise good dish; too much level scaling will ruin an otherwise good game.
Concerning the argument that one gets too strong and the game becomes too easy if one would do everything before he sets out on the main quest: well, why not?
Because it gets *boring,* that's why. Gothic 2, for example -- I barely bothered finishing it because by the time I got near the endgame, I felt like God.
The same goes with Fallout -- toward the endgame, I'm at the point where almost every aimed shot at the eyes hits, and almost every hit kills. That means those climactic fights against hordes of supermutants become as tedious as the sewer crawl after Rat Keeng in FO2. All because it's poorly balanced and let me get over-powerful.
If a game offers a main quest with a captivating story (or maybe alluring rewards, or generates otherwise enough interest), then the chances are high that most of the players go along with it before it becomes too easy.
But there's the rub -- once you're powerful enough, the rewards become meaningless. All that's left is the story, and as some of the folks on your side of the fence put it, in that case, why not just read a book?
If the main quest lacks appeal and is too boring/confusing/unimaginative to begin with, then not even level-scaling will save it.
True -- but it can maintain a level of challenge that makes the game worth finishing for gameplay reasons. And it can enhance a well-written, appealing main quest, so that there's more to keep you going than just wanting to find out how it finished. BG2 is IMO the best example of this working -- the story just got better as it unfolded, and the challenges remained tense and varied enough to keep things exciting.
And if someone is so obsessed with completing just about everything else and the game lets him become a demi-god before he starts the main quest, then I fail to see why everyone else has to be punished for it by making levels redundant and turning monsters into doppelgangers of the player's character. That's just a style and a hand-holding which I dislike deeply.
Absolutely. It's an example of badly-done, cack-handed level-scaling, which should be avoided at all costs.
Naturally, that's just my personal opinion and preference. I know others like a more linear, fast and dynamic approach to things, and then level-scaling is probably a good rather than a bad thing.
On the contrary, level-scaling works best at enhancing games with wide-open worlds, lots of optional content, and lots of character-building options.
The mistake y'all are making is thinking that Oblivion represents the only way level-scaling can be done. It doesn't -- it's an example of how NOT to do level-scaling.
(For another example of a game that does level-scaling extremely well, try NetHack, by the way.)