We have used the same letting agent in Dublin for 10 years now to let and manage our house as we live abroad and can't do it ourselves. I chose the agent after meeting with several agents in the area - this one was by far the smartest of them. At first he was very good, then, I think, he started taking us for granted to some extent as we live abroad and it is difficult for us to get a new agent. So I am not entirely happy with him but, compared to agents from hell discussed in the above threads, ours is jut brilliant!
We have never had serious problems with tenants he found for us, and only a total of about 4 months voids (in total) in 10 years, which I think is pretty good.
So I would actually recommend getting an agent, if you are not confident about handling everything yourself. You just need to take care which agent to choose
I also think the tenants are less likely to try something dodgy with a GOOD letting agent than with an inexperienced landlord.
It might be an option to use a good agent for the first letting (to ease things for yourself to begin with). Then see how it goes and whether you will feel confident handling future lettings yourself.
If you are fairly confident you can handle everything yourself, then you don't need an agent. But I would caution against DIY sorely to save money on agent's fees - as getting it wrong as DIY landlord can actually cost you a lot of money and a GOOD agent's fees may in fact be well worth it!