I have played through the italin BB line up the the pre-caio/conte remodel ships and stopped it got way too easy at that point. Now for early on i loved most of the ships but as soon as i could use the single 10" EOC R guns i used them.
If your doing so in blitz they have extremely good range and damage, you can if played right beat any and all ships in a blitz room. Although the spread will sometimes suck the wind from your sails but it can still be easy enough to get 80-100k with them in blitz or GB's. Stick with the single 10" EOC guns with light to normal shells in GB's they have good enough range and damage to provide a bit of chuckles to you when you engage enemy BB's.
Played both lines early BB's, since every ship knows italian now they get chewed first even if you have a bb5 next to you. However if you play smart stick to the middle/north you can still smack an enemy ship or 2 and get good attack not insane but good solid attack. If ya want better attack the AD has extremely high damage output atm per shell so you can 2-3 shot a bb5 with a good hit.
Now the BB2's on both lines are a bit of an improvement but with one only firing 2 triples it seems somewhat lacking but can still do well on it's own, the dante has decent range with moderate damage a good all rounder on the top line and fun to play.
The Caio and Conte dreadnoughts are out in the relm of being way better than the BB 2.5/3 tier they are set in, they have enough guns and firepower to decimate ships in range fairly easy and once you reach them your BB speed will be much better, Caio goes about 40 While the Conte goes about 42 knots with near or above level 76/77 range.
I have seen and used the bb3 and above on the test server and i must say they have a bit up in the high damage relm with range jumps since they are all mostly angle 25 minus the bb6 at 30. Sadly as have mostly finished work on them but have thus far been unable to get the next test server patch so we can finish the work so they can be balanced right to the live server.
I will say this, despite the size increase to the italian BB4 if it gets in range of something expect it to die in 1-2 salvos even if most of the shells miss. The BB5 has high damage a shell but it also has range jump issues.
My advice, stop playing italy once you get to Caio/conte dreadnoughts, otherwise you may get too used to how they play and will more than likely not enough them being balanced, myself im not bothering in NF and am mostly doing test server balance work with a few others in hopes of fixing italy.
In the end it's up to you if you want to or not but as italy is they are still more powerful than the other nations until you reach bb6 which is a bit more balanced than the rest.