Most of my ads begin appearing in the top spots within minutes, but some others (for the same domain) take days and days. I haven't been able to get a straight answer out of an AdWords rep as to why some take so much longer than others.
Over the time, my impression (and my impression only) was that an account would “earn” some kind of trust and therefore be allowed to go through automatic approval process where ads would go through in minutes.
I know cases where brand new ad group would be in premium area in 2 minutes since its creation.
Ads in other, mainly new accounts, would “wait” on a side for quite a bit (days).
Not sure how it is right now, I haven’t created/changed anything I would check on.
If I’m any right, I like it that way. Trusted goes through until it gets abused or pulls up a flag.
That what you’re experiencing now, I hope it will go back to normal soon.