I will be rewatching some episodes in the future. This is my incomplete list for now:

Episode 1.06 "The Fix"

Episode 2.03 "Masquerade"

Episode 2.05 "Bury the Lede"

I would like to discuss those episodes. Many times it has been said that season 1 is dragging and you have to get over it to reach the good stuff in the later episodes. That is not my opinion. Some of my favorite episodes are in season one. Therefore I would like to add Episode 1.04 Cura te ipsum.

Yes, that one was also very good. What made it your favourite episode?

The best thing about PoI are the different plotlines, that is what you rightly mention as breaking the formula. I have watched a lot of series since this show ended but found none that does it so brilliantly. Here you have one topic - the mysterial mobster Elias - and different persons dealing with it: John, who will be suprised at the end, Finch working slowly his way with his electronic tricks and revealing himself to Fusco, nicely done with a smirk, Carter and Shimanski doing it in detectve style and the Russians of course, who know who they are looking for. That is made so good and in a clever way that the viewer never loses track and will have the full satisfaction of the plot twist at the end. And of course it is the beginning of the relationship between John and Elias, which is so unlikely and still possible because they respect each other. And you are right, the aesthetics of the double B's are good, worth coming back to at the ende of season 5.