I've been trying to merge code changes between 2 branches and it's proving to be an extremely frustrating experience because I don't have any tools to make it easier.
Araxis Merge is reportedly amazing but it only runs on Windows and I don't want to deal with the near-useless command shell and terminal window available on Windows. Perforce, which is what we use at VMware for source control, includes a diff tool that does an excellent job of aggressively automerging files but it doesn't allow me to edit the merged file before saving it while I still have a convenient view of the 2 source files.
Guiffy is platform independent and has a good UI for editing the changes as I merge them but it's not very aggressive about automerging changes so I sometimes have to forego using it because I don't want to manually step thorugh dozens of changes when Perforce will handle almost all of them for me automatically.