i used to use adwords few month ago and the average review took max a day. I made my first ad in months on monday morning its now thursday night and its still in review. I talked to live support and they just say it will be done by end of today (they've said that the past 2 days) do they normally take this long?
I've had a new account under review no less than three times in the first week of opening the account - it took me 8 days before I was up and running! Apparently there was an issue with trademarked terms I had selected - but eventually they were allowed.
I know for a fact that it usually does not take more than 48 hrs. It might be delayed because of in house reasons such as overwork by that department, busy couple of days, etc.
It all depends really, ive had ads go through instantly and others take up to a week to review. It's kind of a pain and there really is no way to expedite it unfortunately.