A few changes will take place after May 9 2016. Some of them will change the scenario a bit more then others.
For example, instead of the 308 questions, test takers will have to respond only to 280 in the same allotted time for each block (60 minutes). This means that you will have more time to answer the questions (40 questions/ block) but it will not impact scores.
This is due to the procedure of scoring on the USMLE Step 1. NBME clearly states that:
USMLE weights all multiple choice questions equally within each Step exam. Thus, answering relatively easy questions or relatively difficult questions correctly provides equal progress toward meeting the minimum passing score. This urban myth may derive from a misunderstanding about the statistical methods called equating that ensure that the 3-digit score is comparable regardless of what test form or what time of year a candidate tests. The statistical processes make small adjustments to scores achieved on test forms that contain relatively more or less difficult items. Scores on tests with relatively difficult items are adjusted up and those achieved on relatively easy items are adjusted down. These adjustments ensure that the scores that are awarded are comparable regardless of the particular combination of items on any examinee’s test form and ensures fairness for all test takers.
Some other changes include: text magnification and reverse color feature or image magnification when you click images and graphs.
You can find here a sample of questions to have a sense of what is the USMLE Step 1 all about.
Have a great weekend!