I can't find my Navy Seals Workout book right now (somewhere in the junk heap that is my garage), so I don't know if it's the same one you guys are talking about. The one I had is also geared toward being ready for BUD's.
I tried to follow the program for a while several years ago. As I recall it was fairly time consuming for a guy like myself working full time, going to school, raising a family, etc.
Speaking very broadly, the program was basically high rep stuff with some strength training. Lot's of running and swimming.
The book had core routines that were pretty brutal. A core routine might look something like:
6 sets 100 pushups
6 sets 100 situps
4 sets 50 pullups
4 sets 50 burpees
etc, etc, etc....
You get the idea. They were huge routines that would take an hour or so to do.
Then you'd run A LOT, usually high mileage (6 - 10 miles) with sprint days also.
Of course they swim a good amount also.
A couple days in the weight room.
Basically when I followed it I worked out all the time, mostly high rep, and lot's of running and cycling (I replaced the swimming part with bicycling because I didn't have access to a pool nearby). I modified it heavily over time to match my schedule until it didn't really look much like the Seals workout at all.
My advice:
If you have the time, do it. But remember it's a lifestyle for these guys trying to become Navy Seals. It's all they do. Figure out what fits into your schedule and maybe modify it some to make it work.
Good luck.