Is there a setting that allows me to change the tab order in gradebook so I can go across a student's grades rather than down an assignment for all students?
No there isn't. However, a series of interface improvements are in the works, which will allow you to use the grader report more like a spreadsheet, with instant updates etc. Some of these improvements will be backported to 1.9.
Thanks Nicolas, I've only recently had a look again at the 1.9 gradebook and it's come along way from the early versions in 1.9 that I saw. Thanks, I don't suppose you know the answer to my other query in this forum about the grade_items_history table getting 4 entries for every new manual grade item do you?