This episode is great for oh so many reasons.
First of all, we see Sonny going to jail only because he is unwilling to tell the name of his informant, so, once again, we see that he is the very best cop as well as a great human being.
Second of all, Gina, working undecover as a hooker, has to sleep with a sleezy guy Lupo Ramirez not to blow her cover. Very emotional, this is the tearjerker moment. Very touching to see how Sonny holds her in his hands after everything is finally over.
And last but not the least, the cast is great. Here we have a young Michael Madsen playing Sally Alvarado (not much screen time though), Terry O'Quinn, who got famous after the role of John Locke on Lost (he had many unappriciated appearances on screen before that by the way) playing Alvarado's lawyer, and of course Burt Young (the guy who played in Rocky) as Lupo Ramirez.
Now about the bad part (and that's why my grade is only 8). 90% of the episode is developing nice and easy but the last ten - way too fast. Cinco gets shot and agrees to give info on Alvarado, our guys get Alvarado, who spills some juice on Ramirez and bam! Top of the iceberg is in cops' hands. All that in 5 minutes or so. I don't like that kind of development.