I will do an interval workout this evening after work. PM is very useful!
Tomorrow evening, another interval workout. Same as above.
Wednesday evening, recovery ride. Same as above.
Thursday evening, 3 hour big climbing ride. I probably won't look at my numbers much during the ride, but I will analyze data after the ride.
Friday, another recovery ride. PM is very useful!
Saturday, fast group ride. Again, I won't look at numbers much during the ride but I will analyze data after the ride. Having a good grasp of RPE is important to me as well as PM data to chew on.
Sunday, rest day to focus on other important things.
Over time, this approach gives me a lot of power information to look at and work from going forward. Much more meaningful that what I would have with HR only.
Is a PM worth it? Very much so to me!

If you want a good read, I recommend this: The Power Meter Handbook by Joe Friel . The other book previously mentioned is really good, but very advanced for someone just considering whether to get a PM.

BTW, there are a lot of people out there with power meters that really don't use them. They will tell you they do, but they don't! They would do well to read and apply the book I linked to also.