I think 100+. Can't check right now though so I'm not sure.
Had two Rush games at 50 - 60. Was trying unlock AA Missiles for the Artillery, and thought I'd just finish the game and get an easy win, then stayed in for one more easy win. Its probably the lamest thing I've ever done in Battlefield 3. Won't use it again, at least to that extent. Sure its fun to get kills, but its way more fun Rushing a base, and destroying an M-Com with my Squad.
“Burn down your cities and leave our farms, and your cities will spring up again as if by magic; but destroy our farms and the grass will grow in the streets of every city in the country.”
- William Jennings Bryan