These are my results so far:
Genial Writing - Got it working. Can't see any way to configure line widths, or the size of text. Gave up. Uninstalled.
Handrite - seems fair - Free version has ads. Pro version available on the Amazon Marketplace, but not the free version. Might continue to test.
FreeNote - most promising so far. There is still a lot that I don't understand about the app, and a lot of options that I haven't explored. But I had the impression I could actually take reasonable notes with it if I could just figure it out. Apparently it is shareware. I didn't see any ads.
[update] just noticed I could have saved myself the trouble and download the APK from the developer's site:
http://suishouxie.com/
PenSupremacy - did not try yet - No free version. I can't seem to get past the idea of paying before testing the program. Not to mention I would be paying to install on my droid and have no idea if the payment status would carry over to the Fire.
Note that I installed all of these using Android Market to my rooted Droid phone, and then copied the APKs over to the Fire. This is an avenue probably not open to a lot of people.