Version 3.15 of the Collatz CUDA application for Windows is now available in both 32 and 64 bit versions. It looks to be approximately 20% faster than v2.03. I'm looking for people to help test it on a variety of GPUs. If you would like to assist and post back your results, it can be downloaded at:

Windows 32-bit: <a href="http://boinc.thesonntags.com/collatz/download/test/collatz_3.15_windows_intelx86__cuda42.zip" rel="nofollow">http://boinc.thesonntags.com/collatz/download/test/collatz_3.15_windows_intelx86__cuda42.zip</a>

Windows x64: <a href="http://boinc.thesonntags.com/collatz/download/test/collatz_3.15_windows_x86_64__cuda42.zip" rel="nofollow">http://boinc.thesonntags.com/collatz/download/test/collatz_3.15_windows_x86_64__cuda42.zip</a>

It requires CUDA v4.2 drivers and must be installed as an anonymous application (a.k.a. using app_info.xml file). Also, optimization parameters have been moved from the command line to a config file so check the README.