You get 3 warnings before you are charged and it is like 20 cents/GB for the overage. I do not like it but in my household luckily we do not exceed the amount monthly. My only other choice is Comcast so I am kinda screwed.
I know but I do not stream Netflix anymore, hardly use YouTube. I keep the 24/3 because I host games on Xbox Live on COD, etc. and I want the highest upload for that reason. I have had all of AT&T's speed packages and this one fits the bill. Comcast is my only other choice and their 20/2 costs more here than AT&T's 24/3. Upload is all I need. I wish they made all their speed tiers with 3mbps upload. Plus with the wife and her laptop, kid with I-pod, and I know someday he will want to play on LIVE so I am all good on speed. I know we will never exceed 250GB but I still think the caps are dumb.