I use this as a command line tool to check exif and do time corrections too, it's a great tool and supports more than images, hell, it will work with pdf metadata, video, mp3, etc...
It also a very easy to use perl library, so it's very nice to program scripts that would need to access the file metadata.
ExifTool is the best tool to deal with EXIF data!
You have to try it to see that. Any type of EXIFs, read/write according the RFC (and sometime more :)) )
Rather fast, though perl. It has anything you could wish.