I had these on my (just sold) Prius. Personally, i love it! DRC (dynamic radar cruise) is a bit conservative at times, but it is like having an extra eye on the road to bail you out...you can easily over-ride the DRC. PCS also tightens your seatbelt which i tested once...it is quite fast and pins you back to the seat instantly...IMO, worth it if you are ever in a head-on collision. I had wanted it on my new car (MDX) but it was too costly for that option.
So, if financial is not a problem for you, then i would get it! Note that you will NOT recover the cost of this package when you do re-sell it down the road...so, buying PCS/DRC is purely for your entertainment/safety. If i had the money, then i would get one with it because i drive on the highway a lot (thus, use DRC daily with my Prius)...and the added protection of PCS for that once in a blue moon catastrophic event. PCS may mean the difference b/w critically injured vs. walking away from accident. With the Prius, i felt that it was a small car on the road...so, i needed all the protection that i can afford.