This agenda does a lot for you as a Corp that other 5/3 agendas can lack in.

It instantly recovers your spent money after scoring. This may be obvious after reading but regaining the 5 credits spent to score is incredibly powerful to keep defenses up on central servers. If you are in credit hell (5-8 credits) it is usually a death sentence to try to score an agenda that will not give you some cash. SSL Endorsement would also fit for scoring with low money.

However SSL doesn’t do quite as good of a job for instantaneous evening of money. If a Corp is trying to land a trace on their turn this agenda does some work. Early game this will put the Corp up +5 (+6 if playing as GameNet) from their current position. That is often enough to ensure a HHN or a SEA Source. Since it just makes the runner poorer after a steal, I would recommend SSL Endorsement if you need it as a source of income.

As another NBN agenda that has an additional cost, making the runner poor can be a potential strategy with Degree Mill and this agenda.

With the additional cost, it can add another secret cost to your remote server that the runner had not anticipated. IAA on a remote with all of the ice rezzed can be dangerous without some additional defenses. This agenda has been quite successful to stop Stimhack runs that had not anticipated an additional 5 coins on top of the server costs.

This is a great agenda and will probably be joining Degree Mill as the only consistently played NBN 5/3s.

I don't like Bellona as a concept. It's not a bad agenda by any stretch of the imagination nor is it an overly strong agenda. What it is is a ridiculously safe agenda. It's a 5/3 Hyperloop Extension that defends itself. If you can slam it down early enough you can score it on thoughts and prayers alone and the opportunity cost to trying is close to zero with only Film Critic or the rarely-seen Whistleblower really countering it. Either the Corp scores 3 points with zero momentum lost since the Runner didn't contest, the Runner steals Bellona and is down 5 plus however much it took to break the Corp's token defenses, or the Runner is short trying to break in and are now down however much it took to break the Corp's token defenses and the Corp scores 3 points with zero momentum lost. It is the 5/3 I have to compare other 5/3's to in yellow since they're competing against what is often a free and riskless 5/3.

I really don't like Bellona as a concept.

One of the best 5/3 agendas in standard play. Runners usually have a pretty good idea how much $ they need to pull off a run. The widespread use of Bellona pushes runners to gather $5 more than they would otherwise need or risk crashing on a Bellona. When the runner is calculating different lines of play, the agenda being Bellona is usually the least pleasant scenario. Every NBN scoring window becomes a little more dangerous with this in your arsenal.

In addition, it gives you $5 when scored, which might make scoring out an agenda feasible in an economically tight situation. Normally, if a money-poor corp does an install-advance-advance, it's probably an NGO Front rather than an agenda, because bankrupting yourself to score a non-winning agenda is generally suboptimal. This makes it easier for the corp to take advance of low-$ scoring windows and harder for the runner to guess what is happening.

Together, Bellona's defensive ability and offensive ability combine into the power of uncertainty. This agenda fits into windows when you wouldn't otherwise expect a 5/3 and as runner you either need to have additional cash on hand to adjust or run the risk that you waste a key run.