My feeling is that if you can get an unused copy of the OG 10th edtion, you should. There are many more resources on this forum and other sites for analyzing your performance on OG 10th questions. I have attached a spreadsheet that I got from Eric. I modified the sheet to be able to tell me where I need to focus and improve. All you would need to do is change the "X"s in the missed columns and the sheet will give you a report of your performance.

I still bought the OG 11th for more practice. As you can see from this site. The more questions you do the better, so if you can do another set of 800 to 1500 questions, even if they are duplicated, then you are that much more prepared.

Hi,
I have taken the GMAT once and score a very poor 570. I think I can go better in verbal. I have already done the OG 10th ed twice & also have the 11th ed. The problem is that I see the questions and remeber the answers (without solving them). Thats the reason why I wanted to get more qs to practice on.

Anyways, I have downloaded the grid you've sent! Thanks!
Juhi