The Wire is awesome, we're on season 5, we would have watched them all by now but a certain toddler and newborn has kept us from watching much of anything!
It is one of the best shows I've ever seen and I'm trying not to be biased being from Baltimore.
About the swearing, I think it would be very disingenuous if they didn't swear. David Simon who wrote the show spent a year on the beat with the Baltimore police as a writer for the Baltimore Sun paper and experienced first hand a lot of the crime and such characters. When you're a drug dealer/taker with little or no education and in the environment you're in that's how you talk.
It can be very hard going. I think one of the reasons it has been somewhat cult-ish and hasn't been on the BBC until now is because of the expansive characters, story line, street talk and intricacies of it all. It can be hard to follow but it does flow if you give it a chance. It's one of those shows where you really have to use your brain and pay attention. It ain't one of these shows on the networks where an impossibly beautiful woman is the detective solving all the crimes week in and week out.
The characters on both sides, police, druggies and otherwise are intriguing and scripted so well. Not sure if Omar has shown up but he's awesome. They even got Method Man from Wu-Tang Clan in there as a baddie