Hi Aditya,
I have bought the paper-based tests, and I can tell you that if you are trying to improve your quantitative score, they are absolutely worthless. These tests are up to 15 years old, and back then, the scoring method was radically different. Missing 1 or 2 problems dropped your score 30-60 points! As such, each test contains about 3 or 4 moderately tough math questions, which are nothing compared with today's tough questions.
If you need to improve your verbal score, however, I think it is definitely useful. It also is good practice when you want to keep your mind in GMAT mode.
If you could use help in Verbal, I think you should buy a set, and see if it helps you.
Best of luck on the GMAT. I know I'll need it!
