After an extensive time (50h) and km (1700km) spent on the home trainer enjoying the benefit of power reading, I have just pulled the trigger on an affordable real power meter. This is for my road bike. Model is 4iiii, left crank based. I wasn't ready to pay $1000+ for the dual sided. Total damage is $390, shipping included. Not too bad.
I have made a lot of progress on my trainer over the last 3 month (over 25% increase of my FTP, that's huge!). I see a lot of benefit with structured training, based on power. It is a lot more reliable then heart rate. Sometimes I see my heart rate remaining low (when I'm tired), it's not a perfect metric. I don't want to lose power reading as I'll get back on the road in a couple of month.
Also, this will tell me my real power values, as the trainer-based power is just calculated estimates.