At last an update exists and I can come back with maybe something worthwhile to say. I have been playing this recent update for the last few days now and I am impressed with all the work that has gone into it. So lets categorize my thoughts here on what I, a lowly player, might have to say. So in my completely unqualified opinion...
Game in General:
-The new music seems fitting in a sense but the old music seems to be gone, or at least I have yet to hear or recognize what was there before. I remember some old music conveyed a very lonely and chilling feeling at times fit for the void where the Flood dwell...and this music seems ambient enough but sometimes seems just odd. I don't really know what to make of it actually, but I guess you can't just ripoff or stick iconic Halo tunes in there because of reasons.
-I find it interesting how you have changed the icons for many standard world types such as volcanic, but in a sense I think I see that you are actually replacing everything with your own version of what type of worlds exist here and any overlap is largely unintended.
-Fleet engagements are more enjoyable somehow, I don't even recognize why exactly either. The impactfulness of weapons I think might be it, as you seem to have made edits to particles and such...most noticeable on the Covenant longer range laser things.
-The difference between UNSC and Covenant slipspace speeds are much more noticeable now, assuming they were not in play before.
UNSC:
-The new starbase is fantastic, plain and simple.
-I do wonder how or what you plan to do with cannon designs potentially emerging for ships, I think the supercarrier got what is suspected to be a distinct look in one of the recent comics.
-I noticed the Prowler is now a Sloop, helps to cement the difference between it and the "heavy prowler" thing that also exists without having just two prowlers.
-The less crazy nukes make it actually more of a challenge now, what with the shiva being a supercarrier exclusive as of right now with the rest getting lesser nukes of sorts.
-I am able to knock a CAS into a stunned spirally state still and have seen it done, but I don't know what is causing it. I thought only the shiva nuke could do that, and it was moved to the supercarrier.
-Not really a whole to lot say on this faction considering it is much more fleshed out than the others are.
Covenant:
-The faction as a whole feels more powerful and not as helpless in the lategame, the added fighters to the CCS and the new models placeholder or otherwise helps to make them feel more like the faction they are supposed to be.
-There are some remnants of the base game's dialogue and unfound strings in places but I'm sure you already know that.
-Covenant ships seem to have much less HP now, but far more shields. I remember in one of the Halo Wars docs way back when a dev talked about how the Covenant base is like a glass house, once the shield fell it shattered pretty quick. If that is what you are going for then I suppose you are accomplishing it. I suppose it fits overall.
-I have to agree with Nyx on the lack of Covenant defensive options. I know that they are supposed to be the aggressors, I know that there should be fleets doing much of the defending work, but isn't that also what the UNSC does? Defending with a fleet? I'm not suggesting that they be able to turtle up to such a degree as the UNSC can, simply that they be given something else besides the hangerbays and starbase to pepper here and there. I know defensive stations are in the lore for them. I think it would help to fill a hole, as they can get stretched thin.
-It seems the Haven starbase has been largely left untouched, so I can only assume changes will happen with it later on as I do find it to be very weak even when fully upgraded.
-It might be something that cannot be helped, but I still think it is so bizarre that the CRS is so much smaller than the CAR despite being its upgrade. The damn thing is so tiny I can barely see it sometimes...its just ludicrous. I guess this is a "damn you 343" situation?
Flood:
-Well you certainly made them even more terrifying so thats a plus.
-I do like how forms practically straight out of the Forerunner trilogy are showing up, definitely makes things more interesting for the game and helps to give them their distinct look.
-The fact that they cannot just straight up infect some of your best ships I think make them less annoying to deal with in that respect. I assume more ships will be like that later on.
-I think this was mentioned before in another topic a while ago, something about if a ship has shields up it shouldn't be able to be infected? I think that is something that cannot be changed if I remember right but its a nice fantasy.
Forerunner:
-I noticed that the infected guardian ships on flood worlds happen to have much higher damage, health, shielding, and armor. I love it, really drives the point home of just how far beyond they were of either of the other factions.
-I poked around in the dev version of the game after muscling through so many errors needing to be skipped, seems you cannot spawn some forerunner ships that are in the game for some reason unless one is using the "spawn all ships" command, I guess its not really much of a talking point but I wanted to mention it anyway.
-I was able to play around with the centurion battleship though, was that actually modified from the last build despite not really being used anyway (that I have seen at least), because it looked like it was edited from looking at its stats.
Well I think that is all I have to say really, much of which has probably already been said. Still, no matter what direction you take the mod I'm sure we will all enjoy it.
EDIT: Oh yeah and red lines and things on Covenant ships...whats up with that?