Aside from technical issues like the single threading, I am a little split over whether or not it's really improved the game enough for me to warrant the purchase. Some good changes, some not, and some trivial. I find the fact it is fully integrated with Steam now to be a plus, but others might see that as a negative.
Things like customized GUIs depending on your faction, while nice to see the first time, are quickly forgotten and I wonder if the development hours were worth it. But then, if they have a GUI specialist on the team, it's not like s/he would have had anything else to do, so I can't say it would have been a waste of time.
I don't really like titans, and I tend to avoid getting them when playing, instead getting more capital ships or other units. I am not a fan of the arbitrary unit rules (only one!) and the predictable fleet usage that they seem to bring along with them. Admittedly this is entirely subjective to how you like to play your games.
I do like the updated graphics, and I do like some of the unique abilities of each faction. Mobile starbases for the rebel Vasari are a bit crazy, but they're fun, and full phase network sharing for all your allies is extremely useful. I never used to play Vasari, now I prefer them by far because of this.
Overall I can't say it's worth the full price if you already have Trinity, but definitely something to pick up on a Steam sale weekend.