The thing about gestures is that they should have consistent behavior across all apps on a platform. Otherwise, they'll be confusing and hard to discover.
As I've mentioned in my comment to the OP, HP's webOS uses sliding pane a lot (it's actually a part of the official style guide). Here're a few screenshots showing how the layout is implemented in apps (native email client and a 3rd-party Twitter client). Scroll below the pictures for recommendations.
The sliding option is indicated by the 3 vertical bars in the lower-left corner of each pane that can be slid. The left-most pane doesn't have any special symbols & doesn't respond to the dragging gesture. Also, note how the right-most panel is shown only partially inviting to pull it out to the full view. In horizontal orientation, the screen width is enough to show all buttons but not enough to display an email entirely.
Now, the left-most pane is hidden. However, there is no visual indicator how many panes are hidden. We know only that there's at least one more pane because there's the sliding icon in the lower-left corner. When the right-most pane is expanded full-screen, there's also no indication of how many panes are hidden.
The first view consists only of 2 panes: navigation & the feed. There's no indication that a 3rd pane can appear (it appears only when you press a tweet and it contains all of the controls for individual tweets). There's also no indication that the feed can slide. Sliding is accomplished by a right-to-left dragging gesture starting anywhere on the pane.
When we maximize the feed pane, the navigation pane doesn't disappear. It slides just enough to cover the labels to the icons but leaves them completely functional, similar to the pattern the OP is using. You can press any of the icons and get to the destination without the panes changing their layout. At the same time, there is still nothing to indicate that the feed pane can be slid to the right exposing more of navigation.
These 2 applications plus the official design guidelines cover all of the interactions with paned layout. The obvious troubles with this approach are 1) indicating the possibility of expanding & collapsing panes and 2) indicating the number of collapsed panes.
Given that such a layout isn't common on Android yet, creating a well-denoted hot zone or a toggling button on the left-most pane (for 2-pane layout) is better than just enabling an uncommon gesture.
Also, if any of the panes goes full-screen with others hidden, there needs to be a clear indicator of how many panes are hidden and which way the user should swipe or press to expose them.