Stable and works.
An excellent and extremely powerful tool-kit for the analyses of ssu-rRNA sequence data. I have used it in the teaching of several metagenomics/bioinformatics practical projects at our university, as well as for my own personal projects. There is no competition, QIIME is simply the best software pipeline for this kind of work.
Once you get past the learning curve, this is an extraordinarily powerful pipeline and tool set for processing and analyzing high-throughput 16S sequencing data. I use it on a daily basis; thanks QIIME developers!