Showtime said that Monday night's fourth-season finale of Weeds drew 1.345 million viewers. Which is true, but over two broadcasts. The initial broadcast at 10pm netted 1.008 million with an additional 337K watching a re-airing at 11pm.
Last year's third-season finale drew 1.025 million across both airings, but I didn't see the split so can only say the combined totals are up more than 30% from last year.
Showtime also has been tracking weekly viewings, where not including the finale, it has been averaging 2.72 million (though I'm not sure that's completely unduplicated viewing, some people do watch more than once) through season four. The weekly average is up 16%, which Broadcasting & Cable says is good news for Showtime since Weeds has already been renewed for another two seasons.