Everyone seems to have that "reliable inside source" feeding them tasty morsels of information about possible release dates for Leopard. For most other rumors, these disparate (and in most cases non-existent) sources would all be saying wildly different things. It gives credence then to both the validity of the tipsters and their rumors these days that they all seem to be saying the same thing; Leopard will be late– at least relative to earlier estimates of when we'd see it.
Infinite Loop over at ArsTechnica breaks down some of the logic behind these new predictions of a later (can you say WWDC?) release, including an analysis of the normal ramp-up to Gold Master production and where Apple seems to be in the process on this cycle. According to one Ars tipster, current builds are "Barely beta."