The official announcement was made by Chris Priestly, Community Coordinator at Bioware:
“The team here at BioWare, working closely with the good folks at Demiurge Studios, has decided that a few more weeks in the studio will ensure we deliver the quality that our fans deserve. The additional time will allow us to incorporate more play-testing feedback, add extra polish and tune the additional features so that Mass Effect is a natural and outstanding PC gaming experience.”
Basically, the delay should mean good news. Let’s just hope the final version of the game proves it was worth wating for.