Who is he:  
2000+ year old dead assassin

Who is he:
200+ year old vampire

Past:
Assassin for His Divine Shadow who killed without mercy

Past:
Vampire who killed without mercy

What changed him:
Acquiring the memories from before he became a mindless assassin

What changed him:
A gypsy curse that gave him a soul

Wardrobe:
Black

Wardrobe:
Black

Hair*:
Amazingly perfect and in place without the aid of hair care products

Hair*:
Amazingly in place and perfect without the aid of a mirror

Intelligence*:
Due to the memories of the Divine Predecessors, he has acquired much knowledge

Intelligence*:
Due to his many years roaming the earth, he has acquired much knowledge

Personality traits:
subtle sense of humor, loyal, feels remorse for what he has done, protects those he travels with, peace loving*, resorts to threats of violence to rescue his friends

Personality traits:
subtle sense of humor, loyal, feels remorse for what he has done, defends those he cares for, peace loving*, only resorts to violence as a last resort, rarely kills humans

Physical Traits*:
The machine side gives him superhuman strength and agility.  He is practically impossible to destroy

Physical Traits*:
The demon side gives him superhuman strength and agility. Though not impossible, he is very hard to kill

His dark side:
When improperly woken up, he gets all homicidal and psychotic

His dark side:
When given a moment of true happiness, he becomes Angelus, and gets all psychotic

Conversationalist?
Hardly.  He speaks when he has something to say.

Conversationalist?
Not really, he's a man of few words.

You might as well knock, cuz this boat won't rock*:
Don't bother luvin this hunk either, he hasn't *functioned* in over 2000 years.  There's speculation about whether or not he has the equipment (I don't care what Season 3 says!  There is still speculation!)

You might as well knock, cuz this boat won't rock*:
This hunk ain't meant for luvin, one moment of true happiness will make him go the psycho route and possibly kill you