The leak has been somewhat of a mixed bag for me; on the one hand, I'm satisfied with the approach BioWare has taken in relation to the inter-species conflicts, on the other hand, some of my favourite characters (Jacob in particular) seem to be behaving to the contrary of how I remember them from ME2.
I can only hope that some of the more ill-advised decisions regarding the plot and characters are nixed before release, if only to ensure continuity between installments. I'm happy to report, however, that the origins of the Reapers and their true motivation are suitably explained, and that those unspoiled by the leaks are in for a treat.
Based on this supposedly "outdated" iteration of the script, ME3 looks set to eclipse ME2 in terms of its storyline and darker themes (the lengths to which Cerberus will go to achieve their ends is truly disturbing), but falls short of ME1's narrative, which I believe to be of superior quality. It's worth noting, however, that the game still has time to smooth-over its rough edges ahead of its March 6th release date.