Hi Young, The latest github should be pretty stable.
Regarding benchmarks, I suggest to start viewing the following resource:
I recommend taking a look at the following previous benchmarks (this is a short list, there are probably many others)
1) Recent academic paper which benchmarks GraphLab vs. Mahout: http://bickson.blogspot.com/2013/07/benchmarking-of-machine-learning.html
2) SC 13 paper which compares GraphLab performance to Giraph: http://sc13.supercomputing.org/sites/default/files/PostersArchive/tech_posters/post152s2-file3.pdf
3) GraphLab vs. Picollo vs. Spark:
4) GraphLab vs. Spark