I still use a basic 24 week approach with 4 six week phases that I began based on Daniels for most athletes that run indoor/outdoor track. We begin in January. (In December they get together to run, but we don't have any structured workouts. For those that run Footlocker, they may take a couple weeks off. )
The first phase consists of two hard days (hills & tempo/steady state) along with a long run. We add a leg workout (Gambetta) on those days as well. The hills (60-90 sec @7% grade) are run hard but with generous recoveries. The other days are basic aerobic days with core strength work.
We race every other week (a total of 4 meets). On weeks without races we also do 8 sec all-out hill sprints @7% grade, providing the roads are in good shape (no ice).
The next three weeks we drop hills and begin long intervals (1 mi @5k pace or 1k @VO2max pace) providing the roads are in good shape.
One change I did make during the first 9 weeks based on Christensen's courses is that even for 1st year runners I will have them go 5 mi at 80-85% of VO2max. With younger runners I had always had them begin with cruise intervals (interrupted tempo) until they could run all of them at the same pace or with negative splits and doubted they could handle the longer (slower) tempos. To my surprise they actually handled them well. I call them "Stillwater Tempos". We don't do them every week - probably every 3rd week.
The next three weeks of the Pre-Comp phase (which also corresponds to the 1st three weeks of our official Outdoor Track season) I transition my top 3-6 kids to Christensen's 9 or 12 day cycles. I add in his 4-minute hills (@2-3% grade. Our track is still usually covered in snow at this point, but if it's available I do have the kids do the flying 30s. The long intervals are done exclusively at 3200m date pace (from an indoor race).
Once we're in the Comp Phase, middle distance runners are running sprint-type workouts that I had never done before (7 x 120m max effort, 5 x 500m at 97% of 400 speed, etc.) I'm still not completely convinced that this is the best long term path for a kid that will eventually be running college XC, but I'm not as against it as I was just a couple years ago either.
As a disclaimer, I should say that one of the reasons I don't try to begin with Christensen's workouts earlier than this is weather related. We don't have an indoor facility and and usually training in snow/ice through the middle/end of March which is a problem for sprint-type workouts.
It's too hard to plan out an entire season for more than 3-6 kids. The 12 day cycle for 800/1600 runners is brutal do workout when you live on repeating 7 day cycles. I try to pick out 3-4 races during the regular season where I expect the very top kids to have great competition. Other than they I set their races to meet the workout goals for that day and add stuff before the meet if necessary. It's not perfect and requires quite a bit of creativity. My interpretation of his work says that his paces are much faster than what I had used in the past and the volume of intense work is much lower.
My experience had been that newbies just don't bring the intensity and focus to hard days necessary to get sufficient benefits from his workouts. I find they do better with Daniels-based workouts. This is true even for older kids that haven't decided to fully-invest themselves - another reason I only attempt to put together a "Christensen Schedule" together for just a handful of my top kids.
I have always adjusted training volumes on hard days to an athlete's weekly mileage (tempo runs - up to 10% of mpw, intervals (5k pace) - up to 8% of mpw, repetitions (1600 pace) up to 5% of mpw), but Christensen doesn't have any such guidelines. Until he published his most recent work that had complete workouts for a season, I had lots of trouble determine how many, paces, rests, etc. for each of my athletes.
I don't follow his plans day-for-day, but I try to understand the key objectives each 9 or 12 day cycle and then lay out the workouts for one athlete at a time. When it makes sense I try to have similar workouts on the same day so the kids can workout together, but that's not always possible.
Every athlete I had on these plans set big PRs this year, including one that set a state meet record. Would they have done so if we stuck with my modified Daniels' approach? Hard to say. I was fortunate to have two Footlocker finalists with the modified Daniels approach during XC and both ran sub-9 for 3200 in the spring. I think Christensen's approach is better for 800/1600 runners, but there's no way to know for sure.
The kids like the lower volume, higher speed stuff more than they seemed to like the longer 3200/1600 pace-intervals that were the foundation of my Daniels plan.