As a long time LoIS player (my main faction since 1.1) i will give a short feedback on the different units from my point of view.
Affendatore: For me this is the most iconic italian unit and the backbone of my army most of the time. It´s pretty heavy in points but has some pretty nice features. The output is quite nice (when undamaged), it has some nice defensive stats (not that common for LoIS) and brings a good amount of TFT´s and Uccisore. The huge shape of the models makes it pretty easy to cover some of our vulnerable mediums for the first couple of turns as well. The major drawbacks on the other side are the AD distribution (output drops pretty fast when hurt) and the danger of boarding (high points combined with SV and low number of AP). Even though boarding can be made harder with escorts and cap this is the main problem since almost each nation has some way to get rid of crew even before boarding.
Mars: Honestly i dont like it that much. The output is allmost the same as the Affendatore (1AD more on raised turrets and broadsides which are useless more than 90% of the games). The output drops even faster (try to use broadsides when damaged) and the 7HP are just not enough. I only use it from time to time because i want to play the model, but in a competitive environment i would always play a affendatore (more activations, HP, and output with Uccisore and TFT´s) or Ballistae instead. The Mars needs a major buff to make it a viable option, maybe a boost in HP and redoutable on some weapons (not sure about this one tbh).
Ballistae: Apretty solid sky fortress with nice defensive stats while being obscured. Fore guns and bomb bays are good. I still don´t like it´s broadsides and the option of area bombardment would be nice. This would give a chance for more positional play and handling enemy corvettes. But overall a nice option.
Minerva: The best unit in the orbat! Hands down this unit brings a frightening amount of AD combined with a calcification generator (my playgroup hates them). The ship is a glasscannon though (even more than other bc´s) and can be boarded really easy so it needs good positional play. Even as an italian player i think this could use a very slight nerf.
Gladius: Our only cruiser brings a high output in closer rangebands and is pretty fragile with only 4HP. I really like the design because this feels how i think of the italian fleet. A deadly fast unit which gives a good punch if they can close the distance safely. The uccisores are a nice option since this is almost the only way of spending remaining points (additional options in the LoIS orbat would be welcome).
Hasta: Now things are getting difficult! Event when obscured it´s way to easy to bring this baby down. The low DR and CR rating combined with the low HP value of most italian units don´t justify spending 100pts. The offensive output is not that great either with the lack of any MARS (except area bombard) combined with the bad fire arc of its fore guns. Compared to heavy bombers of the 7 major nations, this unit needs serious revision!
Pilum: I liked the idea of getting a soutship when the new airbox came out. This gives the option to play a more agressive list with greater focus on boarding. It is pretty fast, brings a nice amount of elite ap and comes with some solid bomb bays. The output of the foreguns on the other hand is not that good. Compared with other orbats they lack either a good amount of AD or good MAR since the bad fire arc doesn´t make this any better. The option for MKII sounds nice on paper, but after my gameplay experience i dont field it to often. The generator can´t be used while being obscured (correct me if i´m wrong) and with a rating of 4/5/5 your enemy can focus the MKII down and score easy 90pts. I would like the addition of a MAR here (maybe air hunter or piercing?).
Fortuna (edited): A very good unit, before they got nerfed in 2.0. With the loss of rangeband 4 and shields they can be shot down pretty easily. Another problem is the torpedos being the only weapon system. Flyers ignore them completly and against anything else your enemy gets to use CC. Since 2.0 they are low level flyers now which means they can ignore enemy fighters which could be really nice (credits to Nazduruk). I´m not completly sure and need more games before i make a final judgement for them.
Cinqueda: I like to think of them as a smaller version of the gladius. They are fragile as well but when they hit the flank of your opponent they can deal serious damage to a squad of smalls or mediums.
Scutum: They have a decent amount of firepower compared to other corvettes. The low AP combined with terror tactics makes this one of the harder to use corvettes. The usage of calcification generators gives your opponent some additional ways to avoid serious boarding trouble. The main strenght is the high survivability though, which makes them a good unit to deal with enemy corvettes and gives the option of some offensive counterboarding.
Stiletto: The output of their foreguns is a bit lackluster. I either play them really offensive and try to draw fire from my other fragile units or cover my fleet against enemy TFT´s.
I think LoIS is a great allied nation with a nice unit diversity. Almost all naval units can be played, even in a competitive environment with the Mars as the only exception. The bigger problem is the aerial fleet though. In my opinion the mediums (especially the hasta) as well as the interceptor (to a slighter extent) could use some revision.