Well, I am pretty familiar with the subject, so let me take a shot at it.
Really, I can't think of a scenario in which simply pausing and then resuming an Ad Group or Campaign would require ads to be reviewed again.
Now of course if you've edited the ad (or added sensitive keywords) during the time the ads were paused, well, then that's a different story. However, the reason for review would have to do with the editorial changes, and not with the pause/resume itself.
So, is there a downside to pausing? Honestly, I can't think of one, except for the excellent point made by eWhisper, who wrote:
I think I posted a few months ago, telling the story of how happy I was to have found a great deal of magazine subscriptions from an AdWords advertiser, while searching at lunch. When I went home later that evening, and went to find the ad again to make the actual purchase, it was nowhere to be found. As a customer, that was really disappointing, I gotta say. Of course, I didn't remember the URL.
One other point: be aware that when you pause or resume there will be a server delay while your change is updated through many hundreds of servers. So maybe resume a half hour before you really must have your ads showing again, just to be on the safe side.