Steps to reproduce:
1) Open Minecraft Launcher 0.5 (Dev)
2) Select an older version than the current snapshot (for example, snapshot 13w16b)
3) Press "Play" button
4) Quit game
5) Exit launcher
6) Open Minecraft Launcher 0.5 (Dev) again
Expected result:
Version Selection dropdown should default to previously selected version (in this example, snapshot 13w16b)
Actual result:
Version Selection dropdown defaults to snapshot 13w17a
Confirmed.