Maybe I'm a bit of a fanatic but I've kept close track of the rate of rental additions to the iTunes store. Here's the available rental count by date over the last two months. Pay very close attention to the last few days! It's about time! 
ITunes Movie Rentals
2/22: 387
2/25: 391
2/26: 398
2/28: 406
2/29: 402
3/01: 403
3/02: 405
3/04: 418
3/05: 428
3/07: 448
3/08: 462
3/09: 462
3/10: 474
3/11: 485
3/13: 499
3/14: 502
3/19: 513
3/21: 517
3/23: 534
3/24: 534
3/26: 542
3/29: 578
3/31: 533
4/06: 586
4/10: 598
4/16: 608
4/17: 610
4/19: 616
4/24: 639
4/26: 658
4/29: 846
4/30: 986
ITunes Movie Rentals
2/22: 387
2/25: 391
2/26: 398
2/28: 406
2/29: 402
3/01: 403
3/02: 405
3/04: 418
3/05: 428
3/07: 448
3/08: 462
3/09: 462
3/10: 474
3/11: 485
3/13: 499
3/14: 502
3/19: 513
3/21: 517
3/23: 534
3/24: 534
3/26: 542
3/29: 578
3/31: 533
4/06: 586
4/10: 598
4/16: 608
4/17: 610
4/19: 616
4/24: 639
4/26: 658
4/29: 846
4/30: 986