An understated expression of a positive mood or otherwise pleasurable emotional disposition; an outcome that far exceeds the standards and/or expectations set forth prior to a defined, goal-directed behavior; an understated expression of awe at one's good fortune or that of another.
It "doesn't suck", when you have a manuscript accepted for publication in a top-tier professional journal; when you win the lottery, get a large pay raise without a proportionate raise in your job's expectations of your productivity or responsibility; getting a minimal criminal sentence rendered by judge or jury that is of far less severity thsn that which was was expected (e.g., probation versus life sentence.
something that is really good but said in a sarcastic way
yeah, the new pool doesn't suck!! or... Just got the new 60 inch plasma, it doesn't suck!!