My first thought was how different the MM warforged was compared to the current dragon version. This makes me wonder if the business model is going to be something like hellgate: you get barebones stuff from core books (because converting monsters to playable races was probably of secondary importance for the MM), but can pay to unlock "superior material" from the online website.
The reason why I am hesitant to sign up is because I have no assurance over the quality of the material I will be getting, or that the info I am receiving will be the type I want. At least with splatbooks, I can first browse through them, and buy them only if I feel that the content inside is useful enough to justify me spending good money on it. For example, the designers may put up rules for playing a true dragon, chock full with racial feats, encounter powers and paragon paths, but I may not be interested in playing a dragon (however well done the article is). I might want more rules for fleshing out my orc or minotaur PC more fully instead.
Also, will we be seeing the online material consolidated into a splatbook which we can purchase in the future? It irks me that wotc would be putting so much effort to doing it right for their online stuff (the warforged article shows that they are indeed capable of churning out top-notch quality material) that they neglect splatbooks.
Indeed, one of my main concerns is that the future splatbooks will not be fully fleshed out, but instead require you to get the online subscription to get the complete set. Might we be seeing scenarios like say, martial handbook having an excerpt stating "For more info on XXX, please refer to the wotc website at ...."