This post goes into details about Wizards or Magic-Users but it also applies to any other spell casters as the changes through editions have been similar.
One of the changes in the more modern versions of D&D has been to fix the “problem” of the old school Magic-Users having very little to do. Old school Magic-Users started at 1st level with a single spell per day. Although the some of the spells were powerful (sleep, charm person) a Magic-User could only use a single spell per day. Once this spell had been used the Magic-User had no armor, a dagger and very few hit points.
To make Magic-Users more fun to play at lower levels 0th level spells were added in 3rd edition which gave a few more spells per day that were pretty weak and mostly useless but still something to do. In the most recent editions (4th and the D&D Next playtest) Wizards have several spells or powers that they can use “at will” or unlimited use. These unlimited spells, while not as powerful as the old school once per day spells are still useful and more powerful then the 3rd edition 0th level spells which could only be used a couple times a day. It sounds a lot better for Wizards these days right?
In the recent games I have been running I noticed that these unlimited spells are actually making the Wizard and the entire game less fun to play. The old school Magic-User had a single spell and usually saved it till absolutely necessary or when it would be the most affective. The rest of the day they had to be creative. They had to think outside the box. Find ways of being useful without spells or weapons. Search the environment for advantages or ways to help the party. This lead to all kinds of unique and interesting actions. Sure sometimes it did some down to throwing daggers at the enemies but more often then not there was other ways to be effective. Now when it comes around to the Wizards turn more times then not the player does not even think about what they could do, just what spell to use. Generally they have one useful spell for most situations and they is what they do. So instead of thinking creatively, looking for advantages or alternate ways to be useful the modern Wizard does one thing, over and over and over. Is this really more fun for the players or the game in general? Instead of looking for ways to take advantage of the situation and the environment (Wizards are almost always the smartest member of the group) the Wizard just casts their one spell again and again. I think this is actually more boring them only having one spell. I think I will do some experiments in my game to see what the Wizards do when they don’t have their same spell to use for every action…