I used to be a big user of OneNote and also have tried Evernote/Springpad as alternatives.
I switched entirely to Google Docs about a year ago and now that Google Drive has arrived the suite is almost perfect for me.
My biggest issue with GDocs is that cut and paste of images does not work reliably otherwise web and screen clips would be easy with ‘Google Screen Capture’ (for Chrome users anyway).
Although labels are now called folders it is still possible to have multiple labels/folders per doc – just control click the names in the organize screen (this is a little fiddly I admit). I find that Google search can usually find what I am looking for without me needing to organize things anyway.
I also find the android app too slow so revert to Catch for note taking when mobile. I expect this issue to go away with next handset upgrade.
Re college documents required to be in MSword. You will never get reliable conversion back and forth – it is a minefield. You can use Google Drive to sync your MS Docs between all the machines that you use. You require MSWord on all the clients (and Google Drive Client) but you get the benefits of sync and 30 day revision history. This is what I used when at college (after many horrible attempts at conversion between linux/various cloud suites/MSWord)