Here are some of the important bits from a brief overview of the Tamarin source code:
JIT Byte Code VM
A high performance just-in-time byte code VM with targets for PowerPC Macintosh, Intel 32-bit and ARM processors on UNIX, Macintosh, and Windows.
Not much to say here, an incremental garbage collector with different implementations based on different strategies. This is an important component for embedded device memory management. This may also be considered for use by future browsers for DOM object memory management especially for Firefox.
If you are working on a browser or mobile scripted apps platform (AJAX, Laszlo, Flex, etc.) platform, this is a huge deal. With Firefox adopting the engine, and its performance and E4X language support characteristics, Tamarin and its offspring might likely become the defacto execution and compatibility benchmark for AJAX and any scripted environments in both desktop and mobile.
The current CVS version doesn’t compile cleanly out of the box on my PowerPC Mac, but I’m sure in a few days, once people realize how big of a deal this is, the project will get whipped into shape quickly.