As announced yesterday, impCentral(™) is now the default UI and IDE at https://ide.electricimp.com which redirects to https://impcentral.electricimp.com (see forum post).
Underneath, impCentral UI is built on the new impCentral API, which supports the new features exposed by the impCentral UI.
impWorks(™), which includes the Sublime Text plug-in, impTest, and the Builder preprocessor is based on the predecessor to the impCentral API (V4 build API) and the legacy IDE (https://legacy-ide.electricimp.com). impWorks is currently being updated to support the new impCentral API and features. We will provide an update on that shortly.
In the meantime, if you have built a workflow around the impWorks tools we suggest you stay with the legacy IDE and V4 build API for a bit longer until the updated version of impWorks is available.
If you have any questions on the transition of impWorks to impCentral, feel free to post these on the forum.