It's surprising that a card as metagame-defining as Audacity hasn't received a review, other than an early on-release review that failed to anticipate how the card would be used. So here's my attempt to bring the reviews up to date.
First, the way Audacity is typically used in practice: it's used in decks that contain 3/2 agendas as a method of fast-advancing those agendas. Install agenda, advance, Audacity, score. (Doing it that way around means that if the Runner has some way to sneak a Clot onto the table, they have to use it after the second click, before you use Audacity, so you don't have to spend the operation or trash the grip.)
Fast-advancing agendas is normally either a) expensive (e.g. Biotic Labor costs 7 to fast-advance your typical 3/2), or b) situational (e.g. Trick of Light costs only 2, but you will need to find two advancement counters lying around somewhere). Audacity is neither expensive nor situational. The cost for the advancement as a whole is 1, and the only time it doesn't work (assuming you have an Audacity and a 3/2 agenda) is if you have fewer than two other cards in hand (something that is rare against most decks – it is usual for Corp decks to have 4–6 cards in hand at the start of their turn). As such, short of Clot or dedicated HQ-trashing (typically by Freedom, Esâ, Alice or Maw), it is basically impossible for the Runner to stop an Audacity score working. This is one of the most reliable – possibly the most reliable – means of fast-advancing an agenda ever printed.
One of the places in which Audacity has been observed showing up, therefore, is in decks which a) might plausibly reach 5 or 6 points with the result of the game still being in doubt, and b) contain 3/2 agendas. It doesn't have to be a fast-advance deck. It doesn't even have to be in Weyland. Frequently this might be just as a 1-of, but it is fairly likely to be drawn before the game reaches 5 points, and it can usually be safely left in hand until that point, helping to blunt HQ accesses (it can't be trashed with the basic action, so only Runners with dedicated anti-operation cards will be able to get rid of it). From that point onwards, the game becomes much easier for the Corp, because there is no longer a need to protect 3/2 agendas in any server other than R&D – if they draw a 3/2, they will just score it and win the game, not caring about the downside because the game is already over. If the Corp can protect R&D at that point, having up to 8 agenda points (up to 14 in Weyland!) effectively removed from the Runner's reach – whilst instantly winning the Corp the game if they are ever drawn – is a huge advantage, frequently game-winning (especially against Criminals). If a deck naturally contains multiple 3/2 agendas, the "1-of Audacity to win from 5 points" is an easy way to improve the win rate of any deck that can afford 4 Weyland influence (and is something that I need to bear in mind when building Weyland decks).
Despite being very strong as a 1-of, Audacity has also been seen as a 3-of, becoming not just metagame-defining but metagame-warping – it turns out that the downside on it actually isn't all that bad in one type of dedicated fast advance deck, the sort that uses only minimal ICE defences, draws lots of cards, and tries to score agendas as soon as they're drawn (in the understanding that any agendas not immediately scored are likely to be lost). When HQ is just as open as Archives, and you're aiming to draw five cards a turn anyway, does it really matter if you're discarding cards from your hand? Audacity has thus become a common sight in Sportsmetal, despite being 4 influence and out of faction – it provides a way to get the 3/2 agendas (which are the ones you really care about in that deck) out of your hand and into your score area whilst only needing one specific card despite the agenda, and the deck is typically quite happy to have random 3/1s stolen. (Before Project Vacheron was banned, it was also typically fine with having the 5/3s stolen, because it was planning to win before the agenda points mattered.) This had a major influence on what it meant to be a tournament-viable Runner deck – you somehow had to be able to stop the Sportsmetal fast advance deck (using either R&D lock or Clot) before it won, and because it won so quickly, this meant you needed to include both appropriate cards versus fast advance, and also enough searching/drawing power in your deck to actually find them in time.
Due to bans (quite a lot of bans at this point!) and the rotation of Dedication Ceremony (the other meta-defining Weyland fast-advance card), there is probably no longer a sufficient critical mass of viable fast-advance cards for the "12 influence" heyday of Audacity to terrorise the tournament scene (although who knows, that deck has a tendency to resurface no matter how hard you try to get rid of it, and even as recently as last week Audacity has been observed as a 12-influence splash even in Jinteki – who knows whether it will catch on). But it still works just fine as a 1-of for finishing games, and there's no reason why you can't still include multiple copies of it if you need a cheap, reliable fast-advance card in your deck full of 3/2s. (This makes me wonder whether it might be viable if you have critical 3/1s you need to score – I'm imagining an NBN deck going turn 1 AR-Enhanced Security, advance, Audacity, score. Probably this is just jank rather than something that's remotely viable, but the power level of Audacity is high enough that I can't be sure, and that's scary.) I expect it to exist in some number in many of the top Weyland decks right up to the point that it rotates out (and/or gets banned), and wouldn't be surprised to even see it show up out-of-faction from time to time.