That brings up an interesting issue that I've been thinking about - if total points remain the same, IMHO an "even Stephen" array is less powerful than a more typical array.
This is because, for the most part 3 of your stats are irrelevant, at least where a class's primary and secondary don't boost the same defence. Yes, there are exceptions (skills, some feet requirements, HP/surges from Con, Initiative from Dex), but for the most part if one has one good stat for a defence, it doesn't really matter what one's other stat for that defence is.
For example, I have a drow chaos sorceress. She has St 8, Co 13, De 17, In 10, Wi 10, Ch 19 post race boosts (D 15, Ch 17 pre-boosts).
With a good dex, what does she need points in int for? Sure, it will boost some skills (knowledge skills, for the most part) and allow certain feets (jack of all trades is nice and needs int 13), but unless I want a "skill monkey", she doesn't need int at all. Therefore, by forcing her (through a mandatory array) to dump dex for int, you are harming her damage output, her secondary effects on powers, her reflex defence, and perhaps skills that are important to her (say, stealth) for IMHO very little
Same goes (and even more so) for wisdom - few skills use wisdom (though, admittedly Perception is really good), few feets that I would be interested in, and any benefit hurts her charisma, which hurts her to hit, damage, will defence and other skills important to her (say, bluff).
Same for strength - other than some skill boosts (to skills which she cares nothing about), strength gives me nothing at the expence of my surges, HPs and fort defence.
Now, admittedly my example character has racial boosts in both her primary and secondary stat, and is in a class where her primary and secondary boost different defences, and there is no tertiary stat (well, asides from having points in something that boosts fort being a good idea). For classes that do have 3 (or more stats - I'm looking at you, Paladin) they need to boost, the even array is less penalizing. On the other hand, IMHO the even array is even more of a penalty on characters that don't have class boosting stat increases, as such characters typically use their race boosts to fill in their weak stats, therefore giving them points to boost their class stats - with an even array you take away that option which basically means that if you want to play a class, you had better choose a race that boosts its stats.
So, if the point buy of the even array is the same, IMHO it offers far less than more typical arrays as it requires the characters to sacrifice stats that actually do something for the character for boosts which do very little. Indeed, about the only thing it has going for it is that it reduces the spread of skill bonuses between party members, which may (or may not) be a good thing for skill challenges.