My experience was similar to minimax. Our tenants were great payers so agents did not need to do anything there.
But they did not look after the house and we had to totally repaint, do the floor boards and replace cooktop. Agent should have seen these things at each 6 monthly inspection but noooooooooooooo. they thought they were doing a fantastic job as they negotiatied a settlement for us instead of going to VCAT but it only covered materials and not labour cost.
So my advice - go for an agent but attend every inspection with them so you can be sure the tenants actually are looking after the property.