Grep the source for "1506" and a priority level. P5 is the highest, most
important stuff. Here's a key:

P0: Toggle mode code. It needs to die.
P1: Feature we could live without/do another way
P2: Mildly useful feature/enhancement
P3: Fingerprinting and linkability defenses; more useful features
P4: Important privacy features, including New Identity
P5: Proxy bypass/state leak issues

These priority levels will also be used to guide us towards a simplified,
toggle-free Torbutton (probably based on Proxy Mobile. See #1506).