¶ Summary
The resistance bonus swap for greater shield size slightly favors the DNI and improves with skills, while the bonus to damage application helps the DNI squash smaller targets and the move away from being locked in to a kinetic damage bonus lets pilots use mission-specific missiles. The DNI also faster and more agile, due to its lighter weight.
In PvE, the DNI is a good choice for blasting rapidly through Level 3 missions.
In PvP, the DNI is mostly known as a ship used for brawling fleets in wormhole space. Wormhole mechanics favor heavy brawls, battlecruiser hulls have a good ratio of DPS potential to mass, and faction battlecruisers are less SP-intensive than command ships. The DNI's seven launchers and its application and range bonuses, mitigating the primary drawbacks of Heavy Assault Missiles, give it tremendous offensive power. Its large buffer tank is difficult to break without a similar composition or capital ships, particularly when backed by Tech 2 logistics ships, most typically the Basilisk.
¶ Skills
Pilots should aim to have Tech 2 shield tank modules and should ensure they have respectable shield skills.
For PvE, typical Level 3 mission fits use Heavy Missiles; if you don't already have Tech 2 HMs, at least train Heavy Missiles to IV and use Arbalest (meta 4) launchers. If you plan on lots of L3s, and/or if you plan to step up to other ships which can use Heavy Missiles in PvE such as the Tengu, it is well worth the further training for Tech 2 launchers. Support skills from the missiles category have a big impact on the ship's performance and the DNI deserves to have them trained to at least IV.
For PvP, typical brawling fits use Heavy Assault Missiles. Having access to Tech 2 HAM launchers will be an immediate priority for PvP, as the extra edge provided by the specialization skill and (in some situations) Tech 2 ammunition can make a crucial difference.