Conceptually, the Warforged are great and fun for Eberron. They're outside the norm enough that I question them before I, say, question Eladrin and Tieflings. Demon/Angelspawn are "close enough" to a fantasy standard that they can be both edgy and acceptable in core.
Constructs are ... sure, somewhat of a D&D "standard". I think D&D and I think Prague when I hear the word "golem".
But "Warforged" as a WORD is evocative of Eberron setting information. It would be akin to Drow being named "Underdarkin". It is a name built in reference to an aspect of their place within a setting ... Warforged, in Eberron, were created to fight a war. Drow, in FR, live in the Underdark. However Drow, in Eberron, live in the jungle. So jungle-dwelling Underdarkin would be odd. Likewise, a race that, in another setting, may not have been created to fight a war ... would be odd with a name like "Warforged".
The bigger issue, though, is something that I hope they fix in 4E.
In 3.5, Warforged are broken. B to the R to the O K E. They get 150% of the healing any othe race gets PLUS they use up 200% of the Clerical healing any other race requires. (Because they get 100% of arcane healing, which no other race gets at all, and 50% of divine healing ... and they require 2x as much Clerical healing. So everybody in a party with a warforged, but the warforged, gets hosed. That your Warforged tank requires 2x the Divine healing of anybody else does not mean he gets less healing, it means the cleric uses MORE to keep that character functional.)
Additionally they're flat IMMUNE to most low-level environmental dangers. And flat immunity changes the game in dramatic ways. A water trap is a minor inconvenience to a warforged. Poison gas is a non-issue. Etc etc. Plus some extreme equipment hazards, for them, are minor damage issues. Ask any fighter if he'd rather lose his Full Plate (or special full plate!) to a Rust Monster ... or if he'd rather take 2d6 damage.
Mechanically they were severely messed up. So, in 4E, they're going to need a total and complete mechanical overhaul. I'm going to say I trust in the designers to do a good job of it, this time around. I'm writing off the 3.5 warforged as an enthusiastic attempt at a daring change, but one that failed. Akin to Two Weapon Fighting in 2nd Ed. (And like 2WF you have enthusiasts that like 3.5 warforged and folks that say "But you can work around all of those issues by totally changing how you run the game!").
If I open up the 4E PHB and find a mechanically unbalanced Warforged in the core races, I'm not going to be upset.
I'm going to be disappointed.
--fje