The season did have its controversial aspects. The portrayal of the angels in particular has challenged a number of traditional assumptions. Some have voiced religious objections, especially to some of the plot twists and statements from some of the angels themselves. To some extent, this could be a matter of misinterpretation of what has been shown, and attributing things to the show that were never meant to be assumed. In some cases, it's a subjective dislike of the direction that was taken. Whatever the case, the effect of that controversy has been minimal; the season was creatively successful regardless.
The fourth season of "Supernatural" earned a Critical Myth Rating of 8.2, which is a substantial gain from the strike-damaged third season. It is also the best season average that the series has gained since its inception. The combination of creative and ratings success is well-deserved, and has ensured that Eric Kripke will get the chance to tell his entire five-season series arc, something that was in serious doubt in previous years.
Ironically, this success has also led to a potential disaster for "Supernatural" fans. The executives at the CW Network are desperate for anything with successful ratings that they have indicated that a sixth season of "Supernatural", with or without Eric Kripke, is a priority. Considering that Kripke's contract will be completed at the end of the fifth season, and thus his intended story will be complete, fans face the unwelcome prospect of a season of "Supernatural" with familiar faces on-screen and a completely new, network-appointed staff behind the scenes.
This puts the fans of "Supernatural" in the unusual position of hoping that the ratings slip once again, just not enough to force the show off the air before the fifth season ends. Of course, fate may be on the side of those committed to Kripke's vision for the show. FOX has tentatively moved "Fringe", a show with much better ratings and promotion, not to mention huge audience crossover potential, into the "Supernatural" time slot. It may well be that fate and circumstance will bring "Supernatural" to its proper conclusion.