The big problem for me with the standard rules is that anyone who doesn't prepare spells at dawn (supposedly most non-good divine casters) gets majorly nailed if he happened to cast spells slightly late during the hours of daylight (ie - the most likely time to go adventuring). Specifically, if someone with a midnight service is forced to cast a spell after 4pm, he can't recover it again the next day. It's even worse if you have a midday service, or heaven forbid a dusk service.
I don't see that as a problem.
That doesn't affect any group more than any other - it just triggers at different times. If you prepare at midnight - it means that you have to start praying within an hour of midnight. So the latest you could start would be 1 AM. That means that anything cast after 5 PM that day is going to jack you.
But if you prepare at Dawn (which I will call 6 AM), the latest you could start would be 7AM. Thus, anything you cast after 11 PM the previous day is going to jack you.
The time period is 7 hours of screwage in either case. If you cast a spell between 5 PM and Midnight you are going to get screwed out of a spell slot if you prepare spells at midnight. If you cast a spell between 11 PM and 6 AM the next day you are going to get screwed if you prepare spells at dawn.
If you are a human, and you normally
sleep at 3 AM, the whole preparing at dawn thing sounds pretty good. But if you are a Kobold, you suffer penalties during the day, so those night time hours are important to you. Getting double whammy for casting spells between 11 PM and 6 AM is
awful - it would leave you only 5 hours of darkness in which you could act freely.
Meanwhile, preparing at Dusk sounds just as good to Kobolds as preparing at dawn did for humans.
And that's balanced. It means that every group actually has a time during the day when they can attack their enemies in such a way as to screw the opposing divine casters. That's why Orcs try to attack at 2 in the morning, and Humans try to attack in the late afternoon.
-Frank