Bukkit

The default config.yml you will see:

dropblocks: true
toolid: 50
respectprotection: true
workatrange: false
breakbedrock: true
countstats: true
serverwide: false
serverwidemsg: true

What everything means:
dropblocks: (true/false)

• This controls whether or not blocks broken in InstaBreak mode drop an item or not

toolid: 50

• This tells you what item to use to break blocks. Default is 50 (a Torch), any item id is allowed, and using 9999 allows any item to be used

respectprotection: (true/false)

• This tells you whether or not InstaBreak will respect Protection plugins such as WorldGuard

workatrange: (true/false)

• This tells you whether or not ranged breaking is enabled globally (Having the permission WILL NOT override this)

breakbedrock: (true/false)

• This tells you whether or not bedrock breaking is enabled globally (Having the permission WILL NOT override this)

countstats: (true/false)

• This tells you whether or not block breaks in InstaBreak mode will count towards your "Times Mined" counter in player statistics

serverwide: (true/false)

• This particular option is potentially dangerous.
  • If set to true, EVERYONE is in InstaBreak mode the second they log in.
  • If set to false, everyone who is able or "/ib enable"d has to be toggled to 'on' before being in InstaBreak mode. This turns off on logout.

serverwidemsg: (true/false)

• This determines if a player is sent a message upon logging in when serverwide mode is enabled