First, I didn't get the return offer even though I believe I did my best and got positive feedback from my manager and mentor. The reasons could be the team is moving at a very fast and intense pace so they are very strict on hiring a new member and prefer senior engineers over juniors. Another reason is the intern return offer is decided by a hiring committee not only your manager or mentor and it's judged by comparing you with all other interns from many aspects. Second, as an intern, I can't take any vacations during the 3-month internship but doctor appointment leaves are allowed. Lastly, there are no other benefits other than the $48/hr salary which I can't say whether it's high or low since it's my first internship.