I do appreciate the hard work that has gone into the new versions and designing the interface. With improvements to the structural changes it may seem like a good idea that the outward appearance should change as well, but this is not a good change.
I often use the IDE for sketching (its main purpose) and just think the simple and minimal look is a nice defining characteristic of the Processing identity. The font choice as well defines the product, even though it's not marketed and sold (thank you for this :) ). Changing appearance too drastically can sometimes diminish a certain quality or perception of quality.
nose_1.1, To deal with the version changes I have renamed most versions to distinguish which one is used. They just show up as this when launching from the dock.
Processing_1_5_1.app
Processing_2_0_b8.app
Processing.app (for current version)
To improve the design I could suggest that the version number be shown on the design from the pre 2.0b9 splash screen. As for showing changes in individual versions through the UI design, there could be another way. Maybe even just showing the version number on the bottom right corner of the GUI?
This is from 2.0b8 and before
sableRaph, good tips!