This chap has now had his date changed 7 times.
http://www.urbanhaze.com/2012/06/complaining-about-bt-infinity-dates-that-keep-changing/
As of today he has registered complaints with Oftel, the ASA, Trading Standards and Watchdog.
Yeah I found his blog today while googling along those lines. Although they do caveat that the dates are an estimate only, it is misleading and you can't expect customers to wait and wait seemingly endlessly to be upgraded. If it's going to be March 2013 or whatever as the earliest true estimate then fine, tell me before I order standard broadband with the intention to upgrade to Infinity.