I've used Hunter Allen's Spring & Winter programs. When I first started training w a PM back in Aug of '06 I followed his program pretty closely and saw gains in all power ranges, from 5 secs to 1 hr FTP.
This past year I crafted my own plan, as I wanted to do well in specific events that demanded specificty and repeatability in certain energy zones. I took some of the workouts from the Spring program and adapted them to my needs.
I've also had the opportunity to discuss my training w select coaches and have received some good advice on how to interpret data; structure my training; et al. While the plans you can purchase on T Peaks are good for building all-around fitness and giving you some structure, they certainly can't replace a coach, especially when you are trying to target a specific event, or series of events, that have specific demands.
Hope that helps.