I was having a lot of problems with Firmata. The major one being with improper versioning of the whole system.
I use Firmata with Max/Msp, Pure Data and Processing, but the different versions of Firmata either had different names, different baud rates or different proctocol versions (even the Firmata official website has documentation for version 2.1 but only distributes version 2.0).
I made the following zip to include my own version of the standard_firmata (based on version 2.1) for:
I corrected a lot
of bugs in all three versions, added servo and sysex support and unified the names (they are all called Firmata).
Get it here: http://interaction.danslchamp.org/index.php?n=Arduino.Firmata