GMAC has announced that it will release an additional set of full length computer adaptive practice tests(CAT) that will likely be released in September 2013. These practice tests are in addition to the two free practice tests that are part of the Official GMATPrep Software. GMAC will charge for the Exam Pack 1 along the lines of the GMATPrep Question Pack 1 which currently costs $25. My best guess is that it would include two additional practice tests.
This is great news because the current two free practice tests are not adequate for getting ready for the GMAT exam. Most students had to resort to computer adaptive tests created by test prep companies, which suffer from a host of issues: poor quality questions, incorrect score predictions, copying official GMAT questions, incorrect distribution of question topics, and the list goes on. For example, I have seen 6 questions on distance/rate/time in a computer adaptive test from one of the major test prep companies. On an actual GMAT test, you can typically expect either two, one, or none. Similar errors are fairly common in CATs produced by test prep companies. My general advice has been to stay away from these CATs.
Let's hope that the GMATPrep Exam Pack 1 would solve bulk of these issues.