Atomic XOR or Atomic O_APPEND in memcached?

[webmaster at generalsynthesis.com]

Hello,

I am using memcached as a form of transactional memory for a
distributed statistical datamining application, and I'm in desperate
need of an atomic append or atomic xor operation.

I noticed an 'append' branch in the Memcached SVN repository. I'm
assuming this is some sort of 'atomic append' patch?

Can someone speak to the performance and reliability of running the
append patch in a production environment?

How does the client protocol change when the atomic append patch is used?

I'm running Memcached 1.2.0 on libevent-1.3b.

Thanks in advance!