Zappo: This is true, but it also makes Young Adult Dragons that are Epic feasible (which, for some folks, is ideal!). It's also how I handle aquired templates (like lycanthropes), since the ECL boost puts infected PCs above the rest of the party.
Another key to making it work is to eliminate "hampered" maturity. For instance, it's been argued (to some degree of success) that Elves are an inferior species because it takes them over a century to reach the physical and mental maturity of a Human. I tend to agree with this assessment, and as such, longer lived races tend to reach physical maturity much earlier (Dwarves at 20 rather than 40+, for example).
Another issue (almost a tangent, but I'll bring it up here anyways and start another thread if the conversation pulls too far from the Planar Handbook) is that of high Hit Die racial conversions. For instance, in 1E and 2E (until the Complete Humanoids Handbook, at least), leveling non-PC races was, at best, a house rule. As such, some races were created at higher Hit Die just to ensure that they were as tough as myth made them. Firbolg, as an example, had 12 Hit Die. In 3E, they are converted (in MMII and at SG's Creature Catalogue) at 13 Hit Die. Question is: Is this really necessary in 3E/d20? After all, is having the Firbolg at 13 Hit Die better than having them at 4 Hit Die with 6-7 Class Levels? This lowers their ECL and makes them far more customizable prior to Epic Levels (which can't be a bad thing, eh?).
Vocenoctum: Y'know, every time WotC puts out a supplement, I sometimes wonder if they've got folks following me around... Gawds know how many times I got flamed on at a certain official site for suggesting something, and now half of those suggestions are in
Unearthed Arcana. Heck, I remember suggesting handling Lycanthropes as a Prestige Class (Requirement: Infection) quite some time before
Savage Species was even a consideration.
Paranoid?

Perhaps... But definately frustrating and kinda ironic.
Of course, that's one of the reasons I'm less uptight about the anti-house rules crowd these days; knowing that at any time a house rule is only a supplement away from vindication does a lot to soothe one's nerves.