Advantages/Disadvantages of using humanity

Hey everyone, firstly I'd like to apologise for not updating in so long. I have been playing a few other RPG games, but recently started a new game as a cleric in preparation for the DLC. Today I wanted to discuss the benefits of being human in Dark Souls. There seems to be rather a lot of confusion online and I have seen several comments on forums claiming things that are later proven wrong.
Before I begin new players should note that I (and presumably most players) will spend the majority of the time playing hollow. This means that you look a bit like a zombie because you either a) haven't used any humanity since escaping the Undead Asylum at the start of the game, OR b) you died whilst human and reverted back to a bonfire [thus] as an undead. There are a couple of main reasons that most players spend a lot of time playing hollow:

1. Humanity if relatively hard to come by (though each boss now drops 1 humanity, and they have increased its drop rate from the system update)
2. Even when you have humanity you may not want to use it due to its rarity, and instead will save it for later points in the game (this can be wise)

So, why would you want to use humanity in the first place? Well there are a number of reasons which I will list below, some of which may mean the difference between life and death in some battles; and others being cool features of the game which you would otherwise have no way to access.
Beginners should note that in order to become human you must have used humanity (so that a number is visible in the circular humanity pool in the to-left beside your health bar) and then visit a bonfire to become human once more. Therefore using humanity and being human are two separate things. Also, not all benefits of using humanity require you to actually be human. Beginners should also beware that if you die after using humanity, unless you can reach your bloodstain before dieing again, you will loss the humanity alongside any souls you may have had.

Advantages:

• You can kindle bonfires (as long as you have obtained the rite of kindling) whilst human, therefore receiving extra estus flasks when resting at that specific bonfire. Note: Kindling carries through to your new game plus, and so forth, so it would be a good idea to at least kindle some bonfires before completing the game to make your second playthrough slightly easier.
• Summoning (co-op): Summoning is one of the coolest features in dark souls, and is ONLY available when you are in human form. You will be allowed to view other players white soapstone marks and summon them to your realm to fight up to, and against, a boss with you. Note: players do not have to be human in order to leave their own white soapstone mark. 
• Item drop rate is increased. Each time you use a humanity you will see your item drop rate will be increase slightly in your stat menu. This benefit is maxed out at 10 humanity (or 210 item discovery), and you do NOT need to be human to gain from this, just to have used humanity so that it is visible in your pool in the top-left of the HUD.
• As well as being able to summon other online characters, you can also summon NPCs to help you fight a boss. Their white soapstone marks are sometimes left just outside a boss chamber before traversing the white mist, and vary depending on which boss you are facing. For example Solaire's summon sign will be seen much more than others.
• You can invade other online players, and leave your red soapstone sign down for other players to accept duels. In order to invade you need a cracked red eye orb, red eye orb, or the aforementioned red soapstone (however the latter requires other players to accept, therefore more like a duel).
• Physical and elemental resistances increase gradually with the use of humanity, and curse resistance is also significantly increased (maxes out at 30 humanity).

Disadvantages:

• You are at risk from losing used humanity when you die.
• Risk from being invaded by other players. You can be invaded in any area (except, possibly, for the Undead Asylum), however this is likely to be more frequent in the forest behind the door in darkroot basin (after using the crest of artorias) as this is where members of the cat covenant will invade you. Other frequent areas of invasion are the Kiln of the First Flame, Tomb of the Giants, and the Duke's Archives - so beware of being human in those areas if you don't want to be invaded.
• Risk of invasion by NPC black phantoms (dark red in colour). In fact these battles are actually fairly easy and once you beat the NPC you will be able to summon them in certain battles to fight for you, and get extremely rare equipment from them which is otherwise unavailable. I almost put this in the advantages section because being invaded by a NPC phantom only happens once (as long as you defeat them) and yields rare rewards.

So that's about it really. There may be a couple of things I missed and I didn't want to be too specific with stat bonuses such as defence and resistance increases as it would have caused this article to be much more exhaustive! Hope that helps clear things up for players who were unsure, and beginners getting used to the game.