Left 4 Dead 2 Forum

From what I could tell melee has always been fairly powerful if used properly,  but pistols have 1 hit kill headshots from long range. Even with terrible aim you could get 5 kills with a single pistol ranged per gun.  The melee are good, but only when an ally does not have a melee weapon and as long you are not swarmed the pistols are superior due to the range.  
 
Pistol have unlimited ammo and take less than 2 seconds to reload and you can melee while reloading. 
 
Melee weapons do more damage and depending on the weapon you could kill multiple but you run the risk of taking damage.
 
Melee helps mostly for newer players with worse aim and it makes it easier for any player when zombies are closer, but pistol have and still are the only way to go if you have good aim. Unless you get the machete although I am pretty sure you do more damage by using melee on the head when holding a pistol.
 
It is bringing a sword to a gunfight and bam...headshot!!

I thought it was a missed opportunity to have melee weapons with unlimited use (as in, no stupid recharge meter before you can attack again), to balance changing the way melee with guns worked from the original game, pre-patch. It would make them a more strategic choice. As it is, it still makes just about as much sense to rifle-butt/pistol whip a group of zombies and then shoot the lot of them. The only use then is the lack of reload times, but then you're pretty much screwed if you use a shotgun and a melee weapon and you're trying to hit an enemy from a distance.
 
Oh, and it seems like melee weapons would be pretty poor against tanks, whereas pistols at least do a little damage.
 
Actually, ratscats made a good point that I never thought of, being a PC gamer only on these titles. Seems melee would have a better use on the consoles, for people not so good at aiming with a gamepad (like me).

@Ulong: Agreed. They seemed like a fun little diversion in the demo, but not a real threat to take the pistol spot for any length of time. After playing through 4 of the 5 campaigns with a buddy, I have to say I used melee more than I did pistols. This game forces you to keep moving more than the first did. Charging forward is much easier when you're able to slice up anything that gets too close. <3 my ninja sword.

I like my magnum whenever I can get a hold of one.  However, I think Ulong is right in talking about some of the big set-piece moments or when you actually need to get somewhere.  I'm still experimenting but have definitely struggled with (I think) the end of part 4 of the Dark Carnival campaign where a horde comes non-stop until you reach the safe room.  You eventually run out of ammo if you don't keep up the pace and this is really tricky with so many zombies charging at you.  I'll try a melee weapon next time I think.
 
As a side note, does anyone know if there's any difference between the machete and katana mechanically.  Is one better than the other?  I'd guess that the katana is faster and therefore better but don't really know.

I always use a melee weapon. I love the awesome sound and feel when you bash zombies with them. They are also handy around alarmed cars.