v0.4.0 highlights, taken from NEWS:

JTAG Layer:

• Support KT-Link JTAG adapter.
• Support USB-JTAG, Altera USB-Blaster and compatibles.

Target Layer:

• General
  • Removed commands which have been obsolete for at least a year (from both documentation and, sometimes, code).
  • new "reset-assert" event, for systems without SRST
• ARM
  • supports "reset-assert" event (except on Cortex-M3)
  • renamed "armv4_5" command prefix as "arm"
  • recognizes TrustZone "Secure Monitor" mode
  • "arm regs" command output changed
  • register names use "sp" not "r13"
  • add top-level "mcr" and "mrc" commands, replacing various core-specific operations
  • basic semihosting support (ARM7/ARM9 only, for now)
• ARM11 should act much more like other ARM cores:
  • Preliminary ETM and ETB hookup
  • accelerated "flash erase_check"
  • accelerated GDB memory checksum
  • support "arm regs" command
  • can access all core modes and registers
  • watchpoint support
  • Shares some core debug code with Cortex-A8
• Cortex-A8 should act much more like other ARM cores:
  • support "arm regs" command
  • can access all core modes and registers
  • watchpoint support
  • Shares some core debug code with ARM11
• Cortex-M3
  • • Exposed DWT registers like cycle counter
  • vector_catch settings not clobbered by resets
  • no longer interferes with firmware's fault handling
• ETM, ETB
  • "trigger_percent" command moved from ETM to ETB
  • "etm trigger_debug" command added
• MIPS now uses fastdata writes Freescale

Flash Layer:

• 'flash bank' and 'nand device' take <bank_name> as first argument. With this, flash/NAND commands allow referencing banks by name:
  • <bank_name>: reference the bank with its defined name
  • <driver_name>[.N]: reference the driver's Nth bank
• New 'nand verify' command to check bank against an image file.
• The "flash erase_address" command now rejects partial sectors; previously it would silently erase extra data.  If you want to erase the rest of the first and/or last sectors instead of failing, you must pass an explicit "pad" flag.
• New at91sam9 NAND controller driver.
• New s3c64xx NAND controller driver.

Board, Target, and Interface Configuration Scripts:

• ARM9 ... ETM and ETB hookup for iMX2* targets
• Add $HOME/.openocd to the search path.
• Handle Rev C of LM3S811 eval boards. ... use "luminary-lm3s811.cfg" only for older boards, use "luminary.cfg" for RevC and newer

Core Jim/TCL Scripting:

• New 'usage' command to provide terse command help.
• Improved command 'help' command output (sorted and indented).
• Improved command handling:
  • Most boolean settings now accept any of the following: on/off, enable/disable, true/false, yes/no, 1/0
  • More error checking and reporting.