GMAC has posted the following notice on the mba.com GMAT scheduling page:
Special Notice for May Test Takers
We are experiencing higher-than-normal GMAT testing for May, especially the latter half of the month. We are doing all we can to increase the number of available appointments; however, for the best chance of testing in May, we encourage you to schedule your appointment now and select a test date that is currently available. If you do not find your preferred test date, please check back frequently or consider a different test date and/or location. If you are unable to find a suitable date in May and your application deadline is in July or later, we encourage you to take the new GMAT exam in June.
If you are hoping to take the exam before the new GMAT (with its Integrated Reasoning section) debuts on June 5, act quickly. Clearly others, many others, have the same idea.
By Linda Abraham, President and Founder of Accepted.com, co-author of MBA Admission for Smarties: The No-Nonsense Guide to Acceptance at Top Business Schools.