I've been catching up on the vastly entertaining "Sex and the City" on DVD over the past few years, buying a season here and a season there, whenever the mood strikes. I usually write a little something about each season after watching it, but at this point, all I really have to add about the series as of the end of season four is this oft-repeated Amazon review phrase: if you've enjoyed the previous seasons, you'll enjoy this one, too. Okay, I'll try to cobble together one new thought: this season is as funny and sexy as previous seasons, but the characters are now deeper and the situations a little more complex. And the good thing is, the added nuance and resonance don't detract from the bawdiness, just make the whole package a little richer.On a somber note, the September 11 terrorist attacks occurred around the time that the fourth season of "Sex and the City" was unspooling on HBO, and it's sad to see the opening credits change somewhere mid-season, to remove images of the World Trade Center. The latter part of the season wisely avoided a major, overt acknowledgement of that terrible day (it really wouldn't have fit in this frothy show), choosing instead to conclude the season with the episode "I Heart New York", a classy tribute to the timelessness and enduring charm of America's most famous city. It worked perfectly.I don't have much else to say about these 18 well-done episodes except for maybe one more of those frequently-seen Amazon review phrases: I loved this season and am definitely on board for the next one.