Well, you also need backups with a "cloud" solution, so that's no difference.
As for monitoring: If you only run it for yourself or a small org, really, you can do just fine without monitoring. If the mail access side breaks, you'll notice, if the inbound side breaks, you'll probably also notice soon enough. But then, setting up a minimal monit that tells you when storage runs low or the MX is down really isn't that difficult either.
So, no, it's not a big project. It's as much of a big project as owning a car, probably less so, if you consider the amount of effort/time required (assuming you have an IT background, obviously).
As for monitoring: If you only run it for yourself or a small org, really, you can do just fine without monitoring. If the mail access side breaks, you'll notice, if the inbound side breaks, you'll probably also notice soon enough. But then, setting up a minimal monit that tells you when storage runs low or the MX is down really isn't that difficult either.
So, no, it's not a big project. It's as much of a big project as owning a car, probably less so, if you consider the amount of effort/time required (assuming you have an IT background, obviously).