Internships are usually a way to find inexperienced people, train them and sometimes decide whether you want to bring them full time. For an employer it is a low-risk occasion to verify intern's skills and for intern it is a great way to learn new things and see how their potential employer works.
I hardly know any situation when an experienced professional went to internships.
Considering all that, when you think about interns you should assume you will probably need to spend more time with them than you would with experienced professionals. It is so basically because they're less experienced so the gap between their skills and your expectations it just bigger. It also means that statistically you need more time to develop interns into full-blown specialists.
On the other hand internships are usually a worthy investment as first, you can teach interns things you want or like, fine-tuning their skills to your needs. They also likely cost you a bit less even once they are developed specialists. Finally, it is a very good way to verify whether they suit your team or not -- you ground your decisions with a couple of months of work instead of a couple of hours of interview.
All in all, I would decide on internships basing on your specific needs:
- Do you need someone adding value fast or you have comfort of working in a longer perspective?
- Do you have enough money to bring up developed professionals or you need to count every penny?
- What is a time perspective of projects you're talking about? Few months or a few years?
- What would be the impact on the project of the wrong decisions in recruitment? Would it harm the project much or you can deal with consequences?
- How much time you can spend supporting new people in the team?
Basically if you have enough time to invest in internships and you think about longer perspective it is usually a good idea. On the other hand, treating interns as a rescue team most of the time makes a situation only worse.