I think part of the issue though is the Gm believing the adventure has been "ruined" simply because the players found a way around many of the challeneges. One thing I learned a few years ago is to reward clever parties accordingly. If they figure out how to beat your adventure in one move, let them. Just like if the players figure out a way to kill your big bad guy in one or two rounds, let them do so.
I think part of the issue stems from players feeling the need to "beat" the GMs adventure (and assume that killing everything is the way to beat it) - might be that there was valuable information that he had put in that tower to actually keep the game going beyond that one session. Might be there were prisoners to rescue that could have branched the story in another direction. Might be the wizard at the top of it who you thought was the BBEG was actually mind controlled by a high level aberation that could have formed an entire new meta plot for the next part of the campaign... guess you'll never know, though.
Of course, folks are now going to accuse me of being a railroading GM for suggesting that giving clues in one session that give the players a direction to go on in their next session is a good thing. You call it railroading, I call it giving a campaign direction... rather than having the players randomly wandering the countryside, killing and pillaging things.
But that's off topic really - so about vancian magic - I don't like it as I've experienced it in Pathfinder.
I'm playing a cleric in my current game - first caster I've played after being a fighter and other simpler classes. Being relatively new to playing a caster in that edition, it takes me about a half hour to actually decide what spells I want in a day every time I get access to a new spell level. And I really don't like the whole rock/paper/scissors casters - if you've got the right spells prepared, some encounters become completely trivial (yep, the caster feels awesome... the guy with the sword and the heavy armour feels pretty useless at the time).
So that'll come under the "Rewards System Mastery" column to some people I guess - I see it more as "assumes or requires system mastery". I don't see that as a good thing - if a new player rocks up to a game and wants to play a Wizard because he thinks they're cool, I don't want to have to say "Probably better not... have you thought about swinging a hammer around? That can be fun too. Yes, those people are playing casters. They've done their time, so they're allowed to have more fun than you"
As they level up, Fighters make choices and stick to them. Rogues make choices and stick to them. So do Rangers, so do Barbarians, so does every other martial class. Why should casters have the right to be ideally suited to any situation, just as long as they know what's coming?
("Hey guess what guys? I've got divination prepared today, I know exactly what we're doing tomorrow!")