The title of an entry is not a string, but rather a GDataTextConstruct. See GDataEntryBase.h for the common methods on entries.
There is a convenience method for setting a title with an NSString. Set the title of a new entry like this:
[entry setTitleWithString:@"Alfredo"]
Also, use the class method
[GDataEntryWorksheet worksheetEntry]
to make a new worksheet entry rather than call alloc/init on GDataEntryWorksheet.