first of all, impl in C++ (JVM/GC is pain in the ass) - clear arch (only master and dataserver) - very concise config file and easy to deploy - most important, 10k nodes scalability without federation design of namespace
Lack of good documentation, no tests and possibly undefined behaviour in a few places. The code also doesn't look any cleaner than HDFS and uses some weird mix of C (*printf, error codes) and C++ (vectors, smart pointers, RAII etc).
