There are a few new features in the latest GBTimelapse release. If you already own GBTimelapse, just download and install this new version. No upgrade is needed.
1) Added ISO calibration tables for the 5D Mk II and the 7D. This feature is enabled by a checkbox in Tools/Options. Using the ISO calibration table can improve AutoRamp reciprocity accuracy and minimize luminance shifts when changing ISO.
2) Added a default f-stop setting to the Camera/Profile. If you use the lens twist method to eliminate aperture flicker, be sure to set this value. It will be used if you didn't take a shot before doing the lens twist and GBTimelapse can't read the Av value from the camera.
3) The AutoRamp maximum ND filter value has been increased from 9.9 to 12.0 to allow the use of 10-stop filters.
4) The 1D Mk IV default camera settings were changed to allow bulb mode shooting.