HI vdm,
I think that everyone would agree that the most realistic and test-like practice problems are the ones provided by GMAC (in that company's various books and online resources) and that everyone's 'goals' include doing the proper amount of practice to hit a score goal on the Official GMAT. However, many Test Takers tend to over-emphasize doing lots of practice problems during their studies (instead of focusing on learning the tactics, patterns and 'secrets' of the GMAT and then applying that knowledge to practice questions).
There is also sometimes a 'skill-related' issue: for example, if a Test Taker's math 'skills' are not particularly strong, then doing lots of practice questions, regardless of the source of those questions, might not be helpful. In that situation, the initial focus should be put on the skill-building (setting up a free account at Khan Academy
www.khanacademy.org, for example).
This is all meant to say that, by defining your specific goals, you can absolutely find what you *need* to achieve those goals. You just have to be specific with the details.
GMAT assassins aren't born, they're made,
Rich