Red Jason has proposed a kind of column where one or both of us tackles popular "myths" concerning 4th Edition. As per his request, I'm going to start things out by talking about the spell magic missile.
A common complaint against wizards in D&D is that, unlike the predecessors, they can cast spells all day. Prior editions had a cap on the number of spells you could cast, most recently modified by having a high Intelligence score. Spell slots were doled out on a per day basis, so once you ran out of actual magic you were powerless until you took a long nap and browsed your spellbook. This was how previous D&D editions balanced mechanics: they limited what you could do each day. The downside is that it lead to the "15-minute day", where you adventure for a quarter of an hour, burn out all your best abilities, and then tuck yourselves in for the next 8 hours or so before having another go.
1st-level spells were really tame, by which I mean that in a lot of cases were inferior to mundane weapons. Magic missile, for example, dealt 1d4 + 1 damage. Period. The average damage output for this was 3.5, while a light crossbow would deal 5.5 damage on average. The only advantage that magic missile had was that it had a long-range-that-you-never-used, and would automatically hit. The downside was that you could only reliably fire off about 3-4 of these things a day. Going by the default encounter-rate-that-no-one-used, you could expect to plow through about 3-4 encounters before necessitating nap-time.
So, you could basically fire off one shot per combat, but 3.5 damage isnt really that useful. Against any typical level 1 warrior monster, you couldnt kill them unless you rolled maximum damage and they had an average Constitution.
What could you do? If you ran out of magic, you were reduced to a really useless almost-warrior. You could fire off a crossbow that wouldnt hit, or try to whack things with a staff that wouldnt hit. Mostly you could end up being a reliability that probably had a better Knowledge (arcana) skill than anyone else.
4th Edition wizards are much different. They have spells that they can use all the time, which has lead some to conclude that they are now magic missile-gatling-guns. This is blatantly false. At best a wizard can reliably loose his magic half as fast as a ranger can arrows, even if you factor in action points. If anything, it was worse in 3rd Edition when a wizard was able to launch multiple missiles per casting. I think the major problem for some is not that they can cast magic missile ever round, but that they never run out of magic. My question is if this is actually a bad thing.
Wizards are supposed to be wielders of arcane power. Is it really so bad that they can consistently fire off minor blasts of eldritch force once every six seconds? Does it somehow destroy the D&D game? NO. If anything I think it makes more sense than a wizard scrambling around his allies trying to avoid getting hit while pathetically loosing ineffectual crossbow bolts at monsters who are spending swift actions to stifle laughter.
Mostly this assertion just screams of nostalgia. You remember the "good old days" when you could only cast one spell each day, and had to leech off of the party so that they could carry you through the dungeon until you hit a point where you were finally useful. You can argue skill uses and social-roleplaying all you want, but scavenging off the success of someone else doesnt sound like a good time to me. I'd rather pull my own weight.