It's more a magi-tech setting than a steampunk one (I don't think there's any steam). The basic pitch is that it's two years since the Great War ended with the largest and most advanced of the kingdoms getting destroyed through magic no one understands and is overrun by critters . There's an uneasy peace with some players (and all the kingdoms are very different) wanting to restart the war, and others just expecting it to be restarted. One of the Five Nations is full of undead that took "I regret that I have but one life to give for my country" as a challenge. There's a bit of alignment subversion going on; the "good" Queen, a just and fair ruler is intriguing to resume the war to bring it to its rightful conclusion, while the "evil" king wants to keep the peace and to clean worse out of his palace and country. And there's an interesting take on most things (in Khorvaire anyway).I want around the game for 3e and 4e, so missed Eberron. I’m not a big fan of steampunk stuff, but is the setting worth a look?
The two big pieces of tech are the Warforged (magitech androids as a PC race) and the Lightning Rail (a rail network that travels across lightning conductor stones both for fast travel from city to city and for train hijacking heists/derailment plots or fighting on top of or tying people to the tracks/stones of). Artificers are a class; it's relatively easy to make magic items and things like everburning torches are everywhere. It's lots of small day to day magic and little overwhelming stuff.
It's deliberately a setting without overwhelmingly powered NPCs; the three accessible ones I can think of are the archdruid, which is a really old tree and doesn't walk around much, the incarnate high priestess (I forget her name) who's a six year old girl and about 16th level in her sanctuary and 5th (and a six year old) outside, and a level 20 commoner baker somewhere in Sharn put in as a joke because D&D 3.X required NPCs to follow PC rules. So the baker is basically really good at baking bread meaning they are 20th level.
(It's been eight years since I last used it so I may not have the details exactly right but most of it is about right).