You can get 40% off with gold BC membership. Lemme see if I can find the code, or if someone else here has it etc...
It's useful-ish. I used it last year when training for Ironman Hamburg. Depends how much you like your graphs and stats, and if you train with HR and/or power then you can get various TSS stats.
I don't have it atm because TrainerRoad has a similar calendar feature now that includes runs and swim instead of just bike, and the plan I'm following is in TR anyway so it populates my calendar.
If I had a coach that used TrainingPeaks then I'd probably sign up again. Especially at 40% off.
Edit: found the code... 2019BC40Gold