We rented a car in Romania and while the car functioned without issues the pickup and drop-off left a lot be desired. The pickup took about nearly 75 minutes all-in, and the drop off person in Sibiu was no where to be found. We called numerous offices and point of contacts, eventually they showed up 3 hours after our scheduled drop off time! Where not sure if it was the company we used or normal (we doubt it), but we'd recommend you have plenty of time on either end just in case.
Also, you might want to checkout doing a road trip on the
Transfagarasan Highway (blog article we wrote about our experience) while you're there, it's a beautiful drive through the countryside and mountains of Romania.
Safe travels!