The main con I can think of are all the extra tooling and dependencies required. However, even though angular-cli is yet another tool, it aims to solve the extra tooling problem so you don't have to know how the tools work and how to configure them. Managing third party dependencies with NPM still isn't fun and can be frusturating IMO, but it sure beats script tags.
I love experimenting with ng-1: make a static HTML mockup; add a stub controller with a sample model and modify the HTML to insert the data and edit things as needed; add some event handlers with dummy actions. (add your REST calls later...)
All of the above can be done w/out any server or compile process - just keep reloading the page when you make changes (perhaps using something like python's SimpleHTTPServer module to serve files from your development directories). Once you get things about how you like them, start on the server side. This approach won't work for a page with a complicated workflow, but you can still prototype quite a bit for an initial learning experience.
