While I can't speak for the other moderators, in my experience as an Ask Ubuntu moderator since August 2010 I can offer a brief glimpse into moderator qualities from my perspective.
If you become frustrated easily, moderation might not be for you. Assuming you visit the site on a daily basis, you'll have to interact with people with whom you may not share the same definition, vision, or belief about something -- Whether that something is related to how Ask Ubuntu should operate, topics acceptable on the site, or even just personal philosophies you have to always be tolerant and understanding despite what you personally believe.
As a moderator you're just one misstep away from being alluded to the subject of Godwin's law. As such, you have to try to always remain tactful when performing actions on the site. You gain powers that not many people will even get close to having and as a result it's very easy to appear you have a "heavy hand" despite the best of intentions. Remaining objective and political in your actions to maintain the appearance of neutrality during moderation can often be a tricky dance.
You're a moderator, which means you were elected because the community entrusts you to do their bidding. As such, remaining neutral and performing actions that fit within the guidelines of a theory of moderation is something you'll have to do on a daily basis. No longer can you simply vote to close something because you don't particularly agree with the subject, now your votes are Stack Exchange Super Votes™. So when you use these new powers, ones you could say come with great responsibility, try to remain neutral and only perform actions that the community would do. This also includes closing "questionable" topics - or too many questions at a time. It's a lot easier to justify a closed question to a user when more than one person has voted on it. So remaining neutral (and not closing a ton of questions with just your super vote) helps to convey the community effort in the site. Basically, just don't be a honey badger.
Always have someone else agree with, multiple people even, in fact make sure meta agrees with you. If you plan on doing something to the site that could be controversial like a new policy, spear-heading some of the worst tags on the site, or even just clarification about what's acceptable always make sure to get a general consensus about your plans and be open to having it shot down, repeatedly, in the face. When dealing with these things it helps to start out thinking you're wrong until proven right. When you do done goofed it's best to just state why you did something and keep an open mind.
It goes without saying, just as you're fallible, so are they. Not everything everyone wants you to do is the right choice. If you have doubts make sure to confer with the other moderators (both on this site and others), as well as the Stack Exchange community team. This is a good way to ensure what's demanded of you is correct and you don't become someone else's puppet.
Something that took a while to sink in: the users aren't powerless without moderators, moderators are powerless without the users. We're here to serve them. You don't own Ask Ubuntu anymore than the next person does. It's a community effort, you're just a tool the community uses when it's needed.
If you're looking for glory or popularity, you won't find it here. If you're looking to scratch an ego, look elsewhere. If you find yourself limited on a daily basis (votes, flags, turn around times) by what you can do to help the Ask Ubuntu community - then apply within. It's a grueling, tedious, near monotonous position where every action you take is scrutinized.