I've been using Jetstrap and Divshot for 2 weeks on a small project. Of the two so far, I've found Divshot has more features and ease of use, yet Jetstrap is very good in its own right. I want to try Easel and I signed up, but the site seemed to be overwhelmed (by Show HN?) and it failed to load for me.
Surely we want competitors in this area, there's obviously a need for it and a number of tools competing on features and price can be good for consumers?
To answer the parent, Adobe technically does have a competitor in this space, though it's not focused on bootstrap and it's kind of complicated: http://html.adobe.com/edge/reflow/
As someone with a product in this space, I'm confident each of the current offerings listed above will diverge sufficiently in the future, specifically in their target audience. It's still so early though.
Surely we want competitors in this area, there's obviously a need for it and a number of tools competing on features and price can be good for consumers?