I've been using Biopython in my lab at the University of Georgia since January 2009. I take an interest in the evolution and structure of regulatory proteins, mainly.
For Google Summer of Code 2009, I wrote the Phylo module to initially support the PhyloXML format, and later generalized it to support multiple formats (inspired by SeqIO and AlignIO). I'm planning to extend these modules to support more formats and common operations as research demands.
I'm on GitHub, too.