You're completely right there. When I'm playing a warforged, and I'm getting down on HP's, I completely have no fear that the resources of that heal spell will ever run out.
Thing is, if the adventure is designed so that the bad guys' main method of depleating your HP is poison or suffocation or starvation or environmental damage or whatever, those aren't valid tactics against a warforged. They can't even get lucky. They can't even get a REALLY POWERFUL poison. Nothing. No blowgun will ever work. The warforged can run into a nest of scorpions without a sweat, or walk through a plague zone nonplused. Even the dwarf barbarian with a +10 Fort save is going to be a little affraid it's something his save can't overcome.
That's really the thing -- I as a DM need to take special account of the Warforged above and beyond what I had to do before the Warforged. I have to make sure that there is a threat in there for the warforged specially. It's not that it's impossible, it's that that means that this one member of the party is basically hogging my DM's attention. And he gets to do that for free.
The warforged have their own special vulnerability: Artificer spells. Which, again, is a note that the warforged basically require a game mechanic all their own (the Artificer) to even be subject to the things that normal PC's fear without it.
Elves are Immune to Sleep Effects.
(a) Warforged are immune to sleep effects and then some...
(b) How many monsters in the MM have Sleep effects? How many sleep effects exist in the game? How many monsters have poison? Disease? Energy drain? How many rely on those instead of high-damage attacks to threaten the party? Not that I'm happy with that particular immunity entirely, but this is like saying "well, he's got a +1, so a +5 should be okay,too!"
And to ghouls' paralizing touch.
Monks and mages are immune to rust monsters.
(a) Elves aren't immune to the paralyzing touch. Warforged are, though.
(b) How many monsters in the MM are rust monsters? How many rust attacks exist in the game?
Things that threaten with poison and energy drain (especially) are archetypal adventuring challenges. Heck, they're what the typical necromancer or assassin uses against his enemies. They come with undead and stealthy monsters quite often. Druids allying with poisonous vermin or snakes or platypi are relatively *common* ideas. Certainly there are other things I could do, but I don't like something as inoccuous and easily solved as a race dictating what I as a DM can and cannot do with my story. With the exception of the warforged (and most LA races, which is ANOTHER thing they share in common), a race choice is 90% cosmetic for the character. They get some skill bonuses, they get some ability bonuses, but even a good choice (dwarven barbarian) isn't a gigantic cut above his peers, and even a bad choice (dwarven sorcerer) isn't a gigantic blow below his peers. The Warforged shares this continuum of not outshining or especially sucking, except in certain specific iconic adventuring scenarios, where regardless of class, they will outshine everyone else.
Just so I'm not entirely ripping on the poor things, here's how they should be "fixed" IMHO, so that they don't push my particular buttons. This is just taking the material from the book and making it palatable, not trying to design a "PC race that is created, not born" from the ground up, mind you.
- Nix the Living Construct thing. Replace it with Humanoid (Clockwork) or whatever. This makes them vulnerable to various BLANK person spells without the enemy having to do special preparation against a different type.
- Nix immunities. Because they are mechanical, they should be better against these things than normal folks; replace the immunities with a +4 save bonus to the things listed instead. Their phsyiology is constructed, but it's very similar to humanoid -- viens that pump oil can still pump venom, gears that generate energy can still get tired, their life force is still something undead can feed on. Keep, for nostalgia and the elf, the immunity to being naseous and the immunity to sleep effects. Makes them fine in swarms, but they have other problems with swarms (like the things not needing to confront their usually-high AC's to hurt them).
- Ditch the half-healing schtick. They're run by positive energy just like any other being. Also (along with some of the other things) removes the need for there to be an artificer in a party with a warforged.
- I don't like leaving the special vulnerabilities to certain spells, but we'll keep 'em in because (a) new tactics can be fun, (b) only specialized enemies will be able to fight against them in this manner, and (c) it is mostly balanced out by the next thing...
- Retain their inability to bleed. This is helpful, but not nessecarily life-saving, in the same way that the vulnerabilities are awkward, but not really condemning.
- They require an energy source. They don't need to eat normal food (I'd allow them to eat rocks, nuts, bolts, metal pipes, whatever), but they need to eat something, and they still require air to make the energy. Let them keep the sleeplessness. It treads on the elves a little bit, but nothing else the warforged does treads on the elves at all, so no big deal.
- They can heal damage naturally, but only do so if they "power down" e.g. sleep. They don't HAVE to sleep, but they have the option if they want to let their inner repair systems take over. They can still heal hp with Craft checks, too.
- They can keep the rest.
And they'll *still* step on the dwarves a little bit, but there's enough differences to make it roughly equal out in the end.
Keep the *exact same* background story, if you like. I wouldn't, but I think the Warforged are set to turn into the next Drow, so perhaps I'm over-sensitive to things that give drama queens the chance to strut their stuff too much. The background is part of the reason that they're so big of an attention hog, but that's something that every DM has to deal with, and it doesn't make them annoying to play mechanically, just with certain kinds of players

It's more of a gripe that Eberron is going to be *defined* by stuff for, of, and about the Warforged more than it will for any other race. IMHO, that's a bad thing, but that's by no means an objective truth -- I just don't like it when one PC race is at the center of attention to the exclusion of others. But there's no doubting that warforged are trendy now, and for good reason. They do have lots of story potential...I just don't value story potential in a PC race.
Whatever their background story, the mechanics for their race as it is makes them awkward, clunky, and problematic. These aren't problems per se, because people will live with being awkward, clunky, and problematic to play a cool race, which the warforged certainly are. They are problems for me (and some others) because I'd rather not have to look up warforged immunities every time I go make an adventure and prepare a backup plan if my original one doesn't challenge this one PC enough.
I don't think that robo-PC's are a bad idea as a race, but I do think they were done in a fashion that makes them abberant and grating here. The problems were so easy to solve, I think part of the reason they didn't was because they felt that the Warforged should be dramatically different from any other race out there. I disagree.