Everyone's needs are going to be different. The reason one should consider switching to Republic, RingPlus or any other service provider is because they would offer more value to your specific situation. It seems the old Scratch model offered much more value for more people than their new model will. Of course not all the details of the new model are entirely clear to me yet, so we'll see.
In regards to Republic Wireless check out https://republicwireless.com/plans/ and scroll left. Their website is confusing, but basically you pay a base $10 for unlimited voice/text over either wifi or cell. If you want data on the go you can purchase 500 MB of data for $7.50 (plus some additional taxes/fees, just like with the Scratch passes). Any data you don't use is prorated and refunded back at the end of the billing cycle. This means you only end up paying for what you use, which is really nice. And if you never purchase a data pass you're only paying a little over $10/month for unlimited voice and text (I hope I'm wrong, but it looks like with Scratch a little over $10/month will only get you unlimited voice, but no texting outside of WiFi). The cost per GB is also cheaper with RW at $15 (with Scratch it ranges from $25-$40), so if you're planning to purchase a pass every month RW likely holds more value for you. However, you have to pay a minimum of $10/month, whereas with Scratch you can pay nothing until you need it. Therefore if you live off of Wi-Fi for the most part (and for example use hangouts/voice for calls) and just have the occasional need for a pass when out and about Scratch may still offer more value to you than RW. And of course you don't have to purchase another phone if you already have a Scratch phone. Just like Scratch, Republic requires that you use one of their phones.
Ting seems attractive if you're looking to use a combination of voice, text and/or data, but in a lot of cases Scratch probably still ends up being cheaper. I like Ting's business model, but it really isn't competitive at the lower end ($6 per line for zero use really is a non-starter for me- if that included some voice or text it might be different).
RingPlus is definitely one I would be cautious with, but it does seem like it could be a viable alternative to Scratch for some people, depending on needs. You need to know what your getting into though. For example they have this radio ring feature where you listen to ads and/or music instead of a dial tone when you call someone.