As far as how WWTB works, each unit focuses on a different type of writing (narrative describing a place, narrative describing a person, dialogue, poetry, etc.) and uses a selection from a famous work as its example. For instance, a portion of Dickens' "A Christmas Carol" is used in the "narrative describing a place" unit as he does an phenomenal job describing the sights/smells/sounds of a London street in winter. The first few days of the unit are used to help students identify descriptive words - adjectives, verbs, nouns - in the sample passage that enhance the writing, making it more than just a humdrum narrative. Then, students are asked to select a place that they know well and brainstorm different descriptive words for that place. Finally, they use what they've brainstormed to write a narrative of their own. Each day's assignment is typically fairly short and students aren't expected to find ALL the descriptive words; it's more an exercise in recognizing them, not a test to locate them all.
With that all said, I really wanted to love it. I loved that the author pulls from excellent literature and I thought that my natural-born writer (currently in CTC) would really love it. Instead, she choked. Every day became fraught with tears over being unable to come up with anything to write. The identification exercises she could handle, but the brainstorming and writing parts just caused her to freeze, regardless of how much help/encouragement I gave her. Even spending extra days on an assignment, her writing was still incredibly flat and stilted, very unlike her other written narrations and even free writing that she does on her own time.
Admittedly, I tend to be rather hard-nosed as a homeschool mom, so I'm certainly an advocate for persevering through something difficult.
But, watching my daughter become completely demoralized in a subject (writing) that she's always loved was the tipping point.
As I looked back at her previous written narrations, I realized that she naturally does many of the things that this author is trying to get students to do - she'll use quotations (from memory, not copying!) and descriptive language in the middle of a WN. She'll take an author's writing style and make it her own. So, I decided the (remainder of) this year was going to be the "year of the written narration". On the days that WWTB is assigned, she either does a written narration from her DITHOR book or her Storytime book. She's getting different genres to work with, different authors to emulate, and learning to hone her personal writing style. Next year, we'll attempt IEW (we've found it to be a good selection this year with our RTR boy). In theory, I like that WWTB has the student write about their "own" topic. My kiddo just isn't quite there yet in that directional process.
All that to say, I will probably attempt it again with my youngest in a couple years, but we'll see how it plays out when she's at that point.