Overall, I'm very glad I bought this. I think it's a great update and very useful, both for myself as a DM and as a resource I can use for my players. I've been trying to run Eberron in 5e for about two years now, using a mixture of my own homebrew and things I found across the web. I found the mechanical options in here to be better (both in function and simplicity) compared to a number of the homebrew elsewhere.
Here are some thoughts on a few sections.
Races: I felt these did a great job at getting the races into the 5e system. Overall, I was very impressed with these.
Dragonmarks: I like that the bulk of these are now an option at first level. I think subraces was a very good idea for how to do the dragonmarks, and it really works to amplify that these are an inborn ability, which may steer you towards a certain skill or class, but does not define you in the same way that your later actions might. The other oddity is that Mark of Finding half-orcs get goblin instead of Orcish. This makes sense with the optional language rule, but doesn't if a DM doesn't adopt that rule.
Aberrant Marks: I like the flavor of this feat much better than just using magic initiate. I wish there was a way for Aberrant Marks to likewise be an option at first level, but I'm not sure how to make this work.
I liked seeing examples of both common magic items as well as some eldritch machines and dragonmarked items.
I am guilty of having first skipped just to the mechanical sections, but I'm really glad I went back and re-read the rest of the text. It was worth
I liked a lot of the various roleplay options presented and the ways to think about actually being in the world.
The chapter on Sharn was very useful for thinking about ways to set different adventures in different parts of the city.
[5 of 5 Stars!]