Great show and "If-Then-Else"[1] is one of the greatest single episodes of any show ever. Like watching the X-Files today, I would recommend skipping a lot of the one-off episodes. Here's a list someone put together.

https://www.reddit.com/r/PersonOfInterest/wiki/index/

[1] - https://www.imdb.com/title/tt4128194/?_ssoLoop=1