To me, it seems very logical to use managed servers. Because it abstracts away some more parts of the whole stack. What do you think?
Managed servers != no root access. Most good managed server providers will give you root and their 'managed service' is to keep things patched, deal with issues that span your cluster, higher tier of support than just making sure the machine is booted and network is available to the device, etc. Sure, there are some providers don't give you root, which brings me to...
Be very cautious of providers who don't offer root and want to do all your app deployments for you. If you subscribe to the "devops" concept then deployment is part of the development process and can't be thrown over the wall and given to someone else to do in isolation. Also, agile methodologies are now enabling us to deploy once a week/day/many times a day rather than the more infrequent cycles enterprise software is used to. These non-root folks are not going to handle a deployment for you on a daily basis. To not give the customer root is to really not subscribe to these new ways of thinking and new ways of doing business.
I would ask why you want to go down the managed server route in the first place? If you need help with your initial setup and deployment find someone in your network to help you on a consultancy basis. Simple on-going server maintenance should be something most technical people can pick up, and if you get stuck go back to your consultant. You'll probably still be better off $$ given the cost savings of managed vs dedicated hardware. Plus VPS and/or EC2 solutions might fit you better than 'bare metal' hardware solutions, but both are (usually) non-managed services.
The only managed services I do recommend is if you want to go down the Heroku route, which is excellent if it fits your technology stack and business. But I don't think that is what you were referring to.
Bugs would arise. Didn't work out.