Also, it's not just important to have a good programme in place but that the teachers are very well trained to use it correctly. A poorly trained teacher or one who is not keen on using synthetic phonics can destroy a good programme.
RWI was produced in a school with a high level of pupils with English as an additional language and has proven effective. Personally I'm not a fan but that's just down to personal preference. As maverick says any scheme is only as good as the staff delivering it and their commitment.
Dd's school currently uses Letters and Sounds and are about to train all staff in RWI to change schemes. L & S has done well by her (comfortably reading white level books at the start of yr 1) and books like Floppy's phonics and Songbirds really gave her confidence as completely decodable, although this has made me wonder whether RWI will prove more effective across the board.