It's gripping, realistic, entertaining, and upsetting all at the same time. I can't do it justice by trying to explain it. This Time Magazine article includes the series in a list of the best TV shows of all time. This San Francisco Chronicle piece calls it a "masterpiece" and says the following about the show:
...the breadth and ambition of "The Wire" are unrivaled and that taken cumulatively over the course of a season--any season--it's an astonishing display of writing, acting and storytelling that must be considered alongside the best literature and filmmaking in the modern era.
Let me warn you -- it's not always (if ever) easy on the psyche to watch and one has to pay close attention to the dialogue. Almost every episode I say to Brad (much to his chagrin), "I didn't get that. Did you get that? Can you explain it to me?" (And I ask all three questions in succession really fast not giving him a chance to answer. As a result, he misses the next few pieces of dialogue himself.) But, that's a discussion for another day.
If you don't have HBO, put the series in your Neflix queue. If you don't get Netflix, go to Blockbuster and rent it. If you actually have a life and do not have time to watch television, what are you doing reading this blog?!