Short version: I would prefer no durability mechanic at all; it's just another potential distraction and problem.
That said, it really depends on how it is implemented. Far Cry 2, for example, has a weapon durability mechanic that is more of an annoyance than anything. Basically, weapons degrade over time, and as they degrade, they become more prone to jamming. Sounds fine, but the speed at which weapons degrade is a little fast, and the only way to fix them is to go to one of the armories dotted around the map and swap the gun out for a good one. That adds up to a lot of travel time, and thus a lot of checkpoints and the many guards that respawn as soon as you are out of sight of the checkpoint. Plus, such a mechanic just doesn't fit the game.
In other cases, the mechanic is much more fitting and much less annoying. Let's take Dark Souls, for example. Weapons slowly degrade over time, and must be repaired either at the blacksmith or, if you purchase the proper item, at a bonfire. Repairing requires souls (which, for those who don't know, are also used to level up), but the number of souls required depends on how much the weapon needs to be repaired. It was an effective and manageable mechanic, and I don't remember ever being annoyed by it.
Dark Souls II changed things, however, and not for the better, in my opinion. The idea was decent: instead of durability being a persistent mechanic, it was restored every time you rested at a bonfire. In order for this to actually have an impact on gameplay, however, weapon degradation could not happen as slowly as in the first game. Unfortunately, the developers sped it up just a bit too much. There were several occasions in which I had to switch to a different weapon while journeying from one bonfire to another simply because in the course of traveling through that area, my frequent scuffles with enemies had worn my weapon down close to the breaking point. Granted, I wasn't always particularly careful with my swings, and striking walls and other immovable objects does more damage to durability, but it was still annoying. The annoyance was compounded by the fact that if a weapon did break, you had to take it to the blacksmith to repair, but while doing so would allow you to effectively use the weapon again, its maximum durability would drop. When you have to include a ring that slows weapon degradation, its possible your degradation rate is just a little too high. (Though I should note, as the game progressed, I found myself having fewer problems with the mechanic, possibly because I was getting better at avoiding hitting walls. Plus, the consumable item Repair Powder allows you to restore some durability while not at a bonfire.)
And then in Dark Souls III, the mechanic might as well not exist. It retained the second game's system, but instead of trying to find a good degradation rate, they just used the (apparently) the degradation rate from the first game, which means that unless you spend the time required to hit every inch of wall or rock between bonfires, you're not going to end up with a broken weapon before you rest at a bonfire. Heck, I've gone past a couple bonfires without resting and have still never needed to use repair powder. I suppose the mechanic might have more of an effect in PvP (like, for example, if an opposing player is using the Acid spell, or something), but in general, I just can't see why it was even included. I'm not complaining, of course, but I'm sure someone's moaning about it somewhere.
