Let's begin with the most important thing: I am a huge fan of this show, and the only reason it gets a "mere" Qualified Recommendation, rather than an unqualified one, is that it's got a very unusual form of presentation, and if you're not the kind of person who is familiar with vlogging, you might find it a bit strange. Of course, you're reading DVD reviews on the internet, so you're probably not someone who will be confused by this format.
For purposes of full disclosure, I should also mention that I know one of the writers, though I wasn't aware she was involved until after I became a fan of the show.
So what is The Lizzie Bennet Diaries? Well, it's an adaptation of Pride and Prejudice, set in the modern day, and presenting Lizzie as a grad student who has set up a video blog as part of an assignment for her media studies degree. If you're familiar with the source material at all you'll know what comes next: an exploration of the lives and loves of the Bennet sisters, particularly Lizzie's own initially hostile relationship with the socially-awkward William Darcy.
The show excels in a number of ways. First, in the delicate balance of its obvious affection for its source material with the need to update and alter characters and events for the new medium and the modern setting. The show establishes its own identity and remains true to its own millieu while still being instantly recognisable as Austen's work. There are many laugh out loud moments dotted throughout, and the comedic elements are judged well: the show is consistently funny when it means to be funny. It can also be very touching and even sad at times. Several episodes manage to juggle humour and pathos with considerable dexterity.
Next is the cast, which is flat out excellent. This was the second time I'd seen the show and if anything I liked the performances more this time than the first. When you're initially being introduced to some of the characters - Lydia and Darcy in particular - you probably won't instantly warm to them on your first viewing. On your second, though, you get to just enjoy what the actors are doing, and appreciate the skill with which they do it. Mary-Kate Wiles as Lydia, in particular, is given the chance to show some great range.
Third is the sophistication with which the show's creative team engaged with their own "new media" format. The show ultimately spanned at least five different youtube channels, plus multiple in-character twitter, tumblr and pinterest accounts. You could simply watch the videos, or dive into all the ancillary elements to your heart's content. I mainly stuck to the former option myself, but I saw enough of the other parts to be impressed by the scope of what they were doing. These are some clever folks.
As long as you are OK with the vlog format, in which the characters largely talk directly to the camera, then The Lizzie Bennet Diaries is a skillful adaptation of a rightly-loved classic, and well worth your time. Best of all, as a web show, it's entirely free to watch every single second of it online. In fact, you can go right here to do so now. And you should.