I believe there was also a major version release (4.8.0) fairly recently. I read some development notes a while back and one of the key features planned for 4.

I believe there was also a major version release (4.8.0) fairly recently. I read some development notes a while back and one of the key features planned for 4.8.0 was a new optimizer based on flow-directed lightweight closure conversion; this is the same technique used in STALIN Scheme, which is widely considered to be one of the fastest known Scheme implementations (i.e., it produces the fastest compiled code). More info on this, for anyone who's interested: http://stackoverflow.com/questions/8859486/other-references-to-how-the-stalin-compiler-brutally-optimizes http://stackoverflow.com/questions/8859486/other-references-...