A couple more cloud-based Selenium alternatives to expand your list:
— Screenster (record-playback, has automated visual testing, and it’s new, which is kinda nice).
— Applitools (also has automated visual testing).
— Usertrace (basically, it’s similar to the two above in the way of overall functionality).
These three are essentially similar to Ghost Inspector (which is the most decent Selenium alternative on your list, imho), but they differ in terms of how the record-playback-verification functionality is implemented.
Anyways, many thanks for the neat article. It’s nice to see that people are interested in this topic!