[jsnell]

Double-tap to zoom in.

Double-tap + drag up to zoom in, double-tap + drag down to zoom out.

Both of these have been in maps for a while, and are a lot better for one-handed use than those Android 1.5-era buttons ever were.

[studentrob]

How the heck is the average user supposed to figure that out? Not intuitive at all.

[jghrng]

Wow, thanks a bunch for that hint!