Mileage may vary here - I hated Races of Eberron because in attempting to expand changelings, warforged and kalashtar I think they changed the emphasis from that which exists in the basic book - and not in a good way.
Some people like the book, perhaps even the majority of people, I don't know

but it *does* introduce changes to ethos in a way that doesn't match the inspiration I received from the ECS write-ups. Simple e.g.s - I like the idea of warforged 'built to spec' as a fighter or rogue model or whatever, rather than the 'tabula rasa' that has to be trained for a particular purpose. The book also includes a number of options for the already strong warforged that make them even stronger. Another e.g. is that a meta-view of Dal Quor 'politics' is given which I find boring and unmysterious compared to the way things are set out in the ECS.
Cheers