I've been using Umbraco for a couple of years now and have several sites on 4.0, 4.5 and 4.7
I've tried following the official upgrade instructions to migrate from 4.0 to 4.5 without success, on several occasions.
http://our.umbraco.org/wiki/install-and-setup/upgrading-an-umbraco-installation

We've just had a discussion about this in the office, and I said that upgrading couldn't be done. Now the boss is threatening to stop us using Umbraco in the future, because of the difficulty/impossibility of upgrading - and I must say, I agree.
I appreciate that it's difficult to migrate a complete working system between versions, but surely there is a way to copy most of the data out of one system and into another using the Umbraco API?
By "most of the data", I mean the Document Types, Templates, and Content tree. And possibly the Datatypes/Users/Members/Stylesheets as well.
Even if I could just do the Content tree, that would be enough to get me by. I can recreate the rest by hand.
Can Courier do this? Can a version of Courier for 4.7 read a 4.0 instance?
Or is there some simpler tool that can just transfer a content tree between 2 instances?