I never thought it got that bad at the end. Certainly not as good, but not Dexter or Heroes levels of declining quality. Then again, it might help that I started watching during the last stretch of episodes. Most dramas seem better marathoned.
Having said that, there certainly are much better shows out there. Even at least one in the specific realm of sci-fi's with overarching plots (Babylon 5).
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"One toot on this whistle will take you to a far away land."
-Toad, SMB3