One of the issues I've seen with the Nid stuff is it is drastically under-priced when compared to other fleets.
For example, compare their upgrades to orks. Orks have to pay 25 points for Super Boosters, which gives them the 4d6 all ahead full, and +5cm spd. Nids only pay 10 points for the +5cm speed. I doubt the cost of the 4th die on AAF costs 15 points.
Same goes for extra turrets, orks pay 20, and nids pay 10. Its the same for nearly every upgrade, nids pay way less for roughly the same bonus.
A nid charybdis battleship can after lots of various upgrades and weapons, cost around 300 pts, and have a similar amount of weapons as another fleets 400+ battleship.
Tyranids might need a full re-pointing for everything, as their entire fleet seems cheaper per ship and upgrade than almost anyone else.
I'm fine with Nids being a nasty close range fleet, but when the entire force gets to double boarding values, add auto fire crits to weapons, ignore shields with lances, use the crazy strong rules for feeder tendrils, and AAF right at you and still fire full effectiveness with cheaper ships, I as an Ork player am better off using my ork models but using Nid rules, as they are a better and cheaper version of my fleet.
Another different matter. One thing I noticed for Orks. The 2 battleships that do not come with Sooper Boosters do not have the option to buy them. And the cost of the Kustom force fields on the kroozers should probably be only 10, not 15, when compared to the battleships 20 point version.
tl;dr Nids are under-priced and a few things about ork upgrades cost and ship options.
Edit: I had never used on and did not realize that the Ork Freebooter Kaptin was the same cost as the other commanders. The +1 leadership is nice, but compared to the Warboss and the Big Mek, he does not do enough. I suggest either giving him another ability in addition to the +1ld or perhaps making him cost less. Maybe +1 ld is fine but other factions get to buy sub-commanders that basically do the same thing for less points, and orks always have less Ld so this ability is not as powerful.