Spell Keys are something that allows a wizard to attune to the plane vibrations, doing this some of his spells may behave normally again. Just physical consideration comes into play with regard to how the spell works now (a fireball in the water still fizzles), but still there are some spell that can’t be cast in certain places no matter what.
The use of any spell key (general or specific) extends the casting period. Any spell with casting time of less than a full round action, becomes a standard action that uses your move equivalent action too (you can cast and move 5 feet in that round) (or 2 partial actions, as you prefer). Also hasted or slowed characters can’t make use of spell keys without taking a full round action to do so (In the case of hasted characters they can cast 3 spells per every two rounds, and still move 2 five foot steps). The effect of spell keys in spells which takes longer than 1 full round action to cast is irrelevant.
For those that haven’t noticed the difference between a full round action and a standard action that uses your movement, please look the Rules Revision.
Now, with the introduction of AD&D 3.5E many spells were modified, created, or deleted. Here's a comprensive list of what is accepted into my campaign (Melroch: "more to come over time..."):
I) All divination spells or items based upon the Scry skill (which no longer exists), now allows the victim a Will save in order to prevent the scrying attempt.
II) The Stat boosters (bull's strength, owl's wisdom, etc) remains the same (Not anymore).
III) With passing time, the full 3.5E spells were introduced and accepted, as long as it doesn't conflicts with what's stated in this website.