The first season is great, the last two. . .less so, but still really good, mainly because Kristen Bell carries the show on her motherfucking back.
If, like me, you watch the first several season 2 episodes and hate them, keep on truckin--that season's suckiness is largely confined to the first several and the last 2 episodes. The season's creamy center is pretty fine. Watch out, that season finale is a doozy of a baddie, though.
Season 3 is even better than 2, but they did away with season arcs in favor of 2 mini-arcs and a bunch of standalones. The season is pretty consistent, with only 1 or 2 real missteps.
Even when the show is at its worst, Kristen Bell (and her TV dad) do a damned fine job of making sure the show is pretty watchable.