EDIT: Now in master
Perhaps the biggest points worth noting here are that:
1) You can now animate Grease Pencil settings such as line thickness, opacity, and colour. Naturally, this opens up quite a few creative possibilities.
2) I've fleshed out the pie menus a bit more to make them (hopefully) even more useful as quick-access type things. That said, for those who do not like these, they are not the primary interface for working with these tools; it is still perfectly possible to get work done without needing to see one at all. Indeed, I've changed the hotkeys to make them a bit less intrusive (i.e. "
3) We have a few more frequently requested tools: Namely, "Bend", "Shear", "To Sphere", and "Select Linked" now work. A few other tools added include "Select More/Less".
4) Proportional Editing settings should now be visible and work everywhere Grease Pencil is supported, provided that you are in "Stroke Edit Mode".
5) Editing strokes on frames where there isn't already a keyframe creates a new keyframe
6) World backgrounds are now rendered in OpenGL renders too. You'll need to enable a separate option to get these to show in the 3D viewport now, but once that's done, they will work in your OGL renders too. (Courtesy of Antony @ BI/Gooseberry)
7) Using Grease Pencil in the Node Editor should be a bit nicer/faster now, since actions there no longer force the node editor to recompute everything (including every single time you move a pixel while painting strokes)