The best part tends to just be the expanded aspects that make sense within the Half Life sphere. There are plenty of good ideas on the world map. This is a massively expanded take on HL which is nice. I really do prefer everyone to have a common slate where characters truly originate from somewhere solid, and may have even shared some experiences in the distant past. I like the timeline as well, what with xen lasting for a little bit, but not too long as to imply humanity just got beaten by the Combine as a default. The map setup is of course really good too, by far the best way something like this possibly could be presented.
Of course, there's lots of other smaller things that you could compliment, but the list would be long and arbitrary, sticking to general things here.
The other good thing about the world is that its base is good enough that it never really loses its potential. No matter the state of the narrative or world, there is always a chance that it can be corrected and brought back to a more positive trajectory. It really is the finer base lore out there, and while it is unmistakably fan-fiction, its base qualifies as being a mostly good fan-fiction.
However, the bad is generally more prominent at this stage of the lore in my opinion, despite that potential.
The Combine are portrayed as being so weak that they more often just feel equivalent to a basic human power that is faltering far more than they do represent anything close to the Combine you see in Half Life. Willard has largely sucked the alien wonder and unrelenting awe from the Combine and replaced it with Oceania, except its much weaker and not trying to make much of a point. Most of the time anything happens with the Combine, its them fucking up something major since 'they are just stupid bugs from space' At this rate, Freeman will be little more than a formality.
On the flip-side, rebels tend to be the absolute worst aspect of Willards lore, partially due to the above. Aside from that, most rebel groups are awfully written, simply put. A large majority being half-baked poorly researched generalizations of whatever region they come from. Russia, for example, has a literal WW2 style Red-Army within it that fights for the glory of communism. Beyond that, the Patriots are just US marines seeking oil to blow the Combine up with and the former HMMLR were brits that only got angry enough to resist the Combine once they publicly executed the queen. Let us never forget the LFC's fucking naval armada either, something that had to be fought tooth and nail to get rid of. Then of course there is the general problem of rebels being constantly able to go toe-to-toe with the Combine in open battle which is just so utterly deflating from a world perspective.
As for the general lore...I don't like how it doesn't so much evolve as it does just rapidly start and stop abruptly. Random sequences of improbable (or impossible) circumstances are pretty much the exclusive measure of Willards storytelling and it really, really takes me out of it. I could compare it to being in a tabletop game with a bad GM. The kind that really has made this large, complicated world and done it well, but just does not have the play-by-play knowledge to make it truly work. So the added complexity of the lore just makes the far simpler and less refined narrative look all the worse.