Of course, the real problem with ECLs is that they aren't a part of the SRD so no one can write anything meaningful about them without IP problems.
Many things that are hardly usable against PCs (like a Tanar'ri's ability to communicate telepathically), and thus give little or no effect on the creature's CR, would be highly usable for a PC, and should thus increase the ECL.
I disagree with that thinking. ECL equals power just like CR does. Telepathy might eliminate those problems where you walk though a gate and meet people who don't speak Commmon, but it sure won't help you in a fight against something.
The real problem is that CR is not linear whereas everything else is. That's why you have monster templates that read "if base CR is 4 or less, template creature CR is unadjusted, if base CR is 5 to 10, template creature's CR is base CR + 1, etc." Is this caused by the XP table being linear? I don't know. And with the D20 license as it is, we don't have hundred's of writer's trying to find a better way to do it. And why do PCs need so much equipment to be "balanced" at their level? Shouldn't there be more inherent abilities?
This is one of the few things that really bug me about the game. Monsters aren't really playable because they don't start out at 1st level and grow in power. My first d20 book (I swear I'm going to self-publish soon or die trying) has a child purple worm in it. It may as well be a whole new monster since I had to guess at things like size, HD, abilities and make up a CR based on the new creature.
Anyway, I've hit too many tangents as it is.
Joe