I couldn't find this comment elsewhere so I though I would start a new thread...
I very much like the idea of 0-th level spells being castable at will.
However, I would like to point out that this creates a situation where pretty much any stellcaster can detect magic at will.
I personally find that this might lead to some abuse. I've never been fond of Paladins having detect evil at will.
I understand that the Complete Mage's Warlock already has this "detect magic at will" ability. It's something that DM's can probably deal with by proper adventure planning, but still, I find this a bit too much. It will tend to trivialize magic detection and, by extension, the whole concept of magic being something mysterious. Basically this pushes the "high-fantasy" paradigm taken by 4th edition and doesn't have the Golarion/Grayhawk feel I would expect.
(My understanding is that 4th edition also allows for detect magic at will through the use of the Arcana skill...)
In any case, I believe getting detect magic at will by default (if you pick that spell in the morning of course) makes the current Magic cleric domain's power for level 2 useless: 2nd Detect Magic (Sp): You can cast detect magic at will.
[Alpha1: Page 54 - Magic Domain]
I must admit I can't think right now of a good way of fixing this...