At one point Anna must have been like any other angel: an emotionless and all-powerful instrument of God who existed only to carry out his orders without question. So in exchange for her free will she had something else entirely - freedom from choice. Never once would Anna have had to worry about right and wrong or the consequences of her actions, because she never had to bother to think for herself. Everything was just God's will. Like all angels, she would have been pretty close to immortal as very little can kill them, and in the possession of an assortment of nifty abilities such as teleportation, super-strength, and the power to bend both time and reality.

Not much is known about the specifics of Anna's life before she fell, but it's a safe bet she was in charge of her garrison as she stated that she was once both Castiel and Uriel's superior. She also spent at least 2000 years on Earth silently watching and waiting for orders from God that she never received, and it was during that time she began to doubt. That in and of itself was a crime punishable by death, but Anna made it that much worse by choosing to rip out her grace and fall, and for that she was marked for execution.

The act of falling wasn't all that fun either; she compared removing her grace to "cutting your kidney out with a butter knife" and literally fell from the heavens at about 10000 miles per hour. But of course she endured it, because Anna had already done something far more amazing - she made her own decision, an act which went against her very nature as an angel. And the odd thing is, the death sentence was never carried out. For some reason Anna was left alone for all those years to live a happy human life, and it's not know if that was because her former family didn't know where she was or if some higher power put a stay of execution on her. You have to wonder if she doesn't still have friends in high places?

Anna's luck only could take her so far, however, and once the armies of Heaven and Hell started to make their moves her human life came to an end. Except I don't think that was the end of Anna's humanity; although she spoke of the emotionless existence of an angel, it seems to me a case of nurture over nature. Remember, she must have felt something in order to fall, even if it was only as simple as envy.

Furthermore, I'm of the opinion that her emotions continued to motivate her actions after regaining her grace, seen in her desire to save the world she loved as well as in smaller things like her interactions with Castiel. Whenever he rejected her it was very clear that she had feelings and they were hurt. Sure, Anna was far more restrained once she became an angel again, but the most dramatic change in her personality I feel came not when she regained her grace, but when she regained her memories. It's more who she is rather than what she is - she went from having only twenty-some odd years of experience to thousands.

That being said, in getting the job done her "angelic" nature really came through. Anna is a big picture sort of person, who relentlessly pursued her cause without hesitating to do whatever needed to be done, be it making eyes at Castiel, killing other angels, or even going on a journey to the past to off Ma and Pa Winchester. And while her emotions got the best of her in season four, it was her angelic willingess to do act for the greater good, no matter how ugly it may be, that finally lead to her downfall.

Anna's Vessel
This is a bit of an aside, but what makes Anna different from any other angel in the series is the fact that she's walking around in her own flesh. All the other angels, Lucifer included, require a person to give them their consent to use their body as a vessel before they can take corporeal form. But by falling and being reborn as a human girl Anna gained her very own meatsuit she would never have to share - there's no poor human riding shotgun in her subconscious. And, although her human body was actually destroyed when she first regained her grace, she called in favours from angels unknown (again, hints at friends in high places) to have it restored, citing sentimental reasons. Other angels (specifically Castiel) have shown no issue with jumping from one vessel to another if need be, but Anna's vessel is living proof of her inability to give up her humanity.

On the subject of her appearance, one thing Anna does have in common with all the other angels is that she seems to be above the need to change (or even launder) her clothes. The outfit she wears as an angel is even mostly the same as when she was a human girl: a white cap-sleeved blouse, jeans, and what I'm assuming is a pair of boots. The only difference is that she gains a spiffy new jacket (a comparison shot of how she dressed both as a human and as an angel can be seen to the right). Perhaps the change was brought about by her floral-print lined number not being considered serious enough for the business at hand, or maybe they wanted to somehow visually express that she had regained her grace. Either way, with her new coat she definitely does look a lot more badass.