I were a bit frustrated with the new design of Responsive Design Manager introduced during the fall and unfortunately it haven’t eased for me since.
What were the purpose of the changes?
The new design made the RDM forgot my previous settings at close/re-open (bug 1332053, 1248619), trashed my saved custom screen sizes, made it laggy only because of centering (bug 1318340) and took away the grabbers for resizing (bug 1342561, appearently you can just drag the border of the window, who knew?).
In return for these mistakes we got a very tiny, very white new UI which takes up alot more precious height space and doesn’t make sense visually compared to the rest of Firefox.
If I’m reading between the lines of bug 1330425 correctly the thought behind RDM v2 could have been to prepare for a multi-viewport layout? In which context the changes makes a little more sense. If that really is the case I’d argue we don’t need a multi-viewport function and certainly not instead of the important basic functioning. Yeah, Sizzy is fun and cool for 2 minutes but it already exists but I don’t see the use practically.
As the issues with RDM v2 doesn’t seem to be fixed I’d vote a regress to RDM v1 until v2 has something positive to bring.