For the most part, I just bought Piledrivers to tear out their cannon, give it to the Omnifactory, then proceed to smother my ship in them. Though, I feel the need to note that for the sake of keeping battles going, I remove the ammo count of the UPC. That way, dragged out battles don't turn into wars of attrition as one side waits for the other to run out of dakka.
The ship itself is okay, if woefully under equipped, even in it's job of basically being a space-borne A-10 and being a gun with a complimentary ship attached to it. I like the Piledriver's design. Though it's two small energy slots barely protect it from anything and the range of the UPC means that the Piledrivers get closer than they need or want to with their limited secondary weaponry.
Nirvash and Jackhammer I haven't much played with, because-
ARGH ASYMMETRY
Though I have played with the Banshee because it looks like a flying sword and it spews forth so many missiles that it was too much to resist putting adv. launchers in every slot I could.
Photon Torpedo Launchers, and Photon Cannons both suffer from an issue which is that flak denies the s**t out of them. While spitting globs of photonic energy at mid and high tech ships is great because all they have is PD lasers or Burst PD, larger low tech ships refuse to be bullied because of their flak guns. Entire bursts of Photon Repeaters can be denied all day long by dual flak, or god forbid, the Thunderchief. I know that's the idea of flak, but yeah. Normal PD seems almost pointless against it, except en masse, while one can shoot down entire photon spreads and even punches massive holes in UPC walls of photonic energy.
Darkmatter Beams, never seen much point in them. The kinetic damage seemed a little low for the length of the burst, though I also have that issue with the big PD laser. Antiproton or some such? It's burst seems very long, it's tracking slow and while it can deny missiles, there is a long time between lazes.
Another nitpick I have is with the Tractor Beam. Why in blue blazes is it a PD weapon? I used it once and for an entire battle, it was wasting my large slots by not-shooting-down missiles and just making them do pretty twirls instead.