I notice throughout the day that the stats in analytics and adsense don't match. Adsense will show a certain number of impressions while analytics will usually show substantially less. By the end of the day, everything evens out and the stats are very close. It's more a vent but wouldn't it be nice if the two matched up.
In my experience Analytics only updates a couple of times a day. It's only really accurate for the previous day's visits.
In my opinion real time stats aren't really necessary. Whatever you want to check today, you can just as easily check tomorrow.
Adsense seems to be counting impressions differently since about a week ago. Where it was counting impressions of different ads on the same page as 1 impression, now it seems to just simply combine the two numbers.