<<...Any other Gotta have? software out there?..>>
...Although you've already mentioned it, I think that OneNote has stood the test of time and is probably the principal gotta-have tablet application. Add Win 7's basic array of accessory apps to that, and you've got a lot of functionality to start off with.
My guess is that beyond this, desireable applications rapidly become the subject of personal needs and preferences. Personally, I still like the same kind of applications for my tablet(s) that I wrote about years ago:
<> A note-taking app: OneNote
<> An office productivity app: Office suite
<> A drawing and sketching app: Currently using ArtRage 3
<> A math / calculation app: Currently using MathJournal 2.1
Along with Win 7's accessory apps, this small number of applications handles nearly all of my needs when I'm on the go...