Having re-read the continuity, I have to admit that the crossovers with Thor and the Eternals are probably the clunkiest parts of the long sequence, although the Celestials make for great villains. Thomas did not actually complete the entire epic, as exigencies forced him to turn over the writing duties to Mark Gruenwald and Ralph Macchio. Similarly, though John Buscema began the sequence, the majority of the penciling was done by Keith Pollard, and may represent his best work for Marvel Comics.
Despite Thomas' legendary commitment to continuity, he drops the ball in the "Seigfried" sections in that he shows how Odin gave birth to Thor by a non-Asgardian mother-- yet somehow tries to imply that Odin's mortal spawn, the Seigfried of the Wagnerian narrative, is also actually Thor by some unexplained logic, rather than being simply the Thunder God's half-brother. Perhaps Thomas meant to use one concept introduced in issue #294, "the Celestial Axis," as a catch-all explanatory device, but if so, he failed to follow up on it, as did Macchio and Gruenwald.
Nevertheless, it's a great romp through the many worlds of the Marvel cosmos.