Here's my solution to the tablet pc angle conundrum...
In this pic, you see it configured for use on a tripod. That's why I have the artist's palette slotted in at the front. Normally when I'm at my desk, I don't slot the palette in. But the keyboard and mouse are standard accompanying dishes.
The tablet all alone on the easel is a bit lacking. I find that I need the keyboard for ArtRage keyboard shortcuts. And for easy entry of file names. Tablet entry works, but it takes too much time under pressure. The mouse is useful for navigating around outside of ArtRage. Things like web pages and such.
Here's a look at the two items side-by-side, showing the tablet in laptop mode, and the easel waiting for inspiration to strike.
I've sawn bits and pieces off the easel, simply to make it fit in my bag for when I fly to Visual Facilitation gigs. (http://snipurl.com/visualfacilitation)
I find that this configuration really suits my needs. And because it's all adjustable, it's very friendly on the neck and back.
If you look for a table easel, I would suggest good art shops. I've seen similar ones to these at Herbert Evans in Joburg. And I got mine from a fleamarket -- the Rosebank Fleamarket, to be precise.
Things to look out for...
o It needs to be portable, and therefore, foldable flat.
o It needs to have sticky-outy-bits that can be sawn off to save space.
o The BACK sticky outy bits need to be fairly long, specifically for when you have your angle closer to horizontal than vertical... the centre of gravity takes over at that point. DON'T saw them off! And be sure to test it with your tablet pc BEFORE you purchase or saw anything.
o Light and small are your friend if you're lugging these things around to coffee shops and onto planes like I do.