PlayStation Now has been a successful platform for Sony with it working across many platforms under the Sony family tree. While it has issues, the service is worthwhile to use and from personal experience, I highly enjoyed my limited time with it. But I would advise not paying for your subscription to use it on your PlayStation 3 or PS Vita in August, as Sony announced the following today.

On August 15, 2017, we will be discontinuing the service on the following devices:

• PlayStation 3
• PlayStation Vita and PlayStation TV
• All 2013, 2014, 2015 Sony Bravia TV models
• All Sony Blu-ray player models
• All Samsung TV models

Additionally, 2016 models of Sony Bravia TVs will be discontinued on April 1, 2017.
After thoughtful consideration, we decided to shift our focus and resources to PS4 and Windows PC to further develop and improve the user experience on these two devices. This move puts us in the best position to grow the service even further. If you use any of the above devices, we want to give our heartfelt thanks for your support, and we hope you’ll continue with us. Remember that all of your PS Now cloud game saves can easily be accessed on both PS4 and Windows PC.

To focus on the PlayStation 4/PC versions of PlayStation Now, support on older Legacy hardware is being axed. This is a shame, considering the PlayStation Vita works wonderfully with PS Now. But you can still use it until the cut-off date that is August 15th, 2017.
Source: PlayStation Blog Post