I usually think it's great to be able to work with a team on a project. However, there can be difficulties sometimes - I'd say the hardest part of working with other team members would be dealing with the different work styles and personality styles of all of the team members. Everyone is different, and so every team needs to develop a specific way of working together so that each team member gets to contribute to the project to the best of their ability. It can take a bit of work to figure out exactly how the team should operate - for example, one team member might like to talk a lot and bounce ideas off of other people, while another might be more quiet and prefer to share her ideas only after she's had a lot of time to sort them though. Just as every person is different, every team is different, and needs to work together to figure out how to be the most effective.
There is also the possibility of being an engineer and working on a team with non-engineers. The non-engineers might have slightly different goals or objectives than the engineers, and it's important that everyone communicates to make sure they're all on the same page!
PhD Candidate in Materials Science and Engineering