I have used Garmin training plans before and had a generally ok impression. Currently, I am getting back to fitness after a year of major disruption, and have just had a month of just under 4 hours a week running plus cycling and weights and some basic fitness.
Anyhow, I decided to do a Garmin 5k plan and picked the Galloway one. I liked that it started with a 5 minute test and a mile test, but the next week is a bit weird. Just two sessions of drills (which could be less than 30 minutes unless I pad them our) before a third test (which is less than 30 minutes running including the warmup and cooldown). Less than 90 minutes runnning seems like detraining to me. I don't think this plan is really suited to me, despite its claims of being adaptive.
I have done at least one Galloway plan a few years back,and the thing I remember about that was long runs that were surorisingly large quantities of run-walk intervals, which I found quite stimulating.