Thanks for your write up 4535jacks, very interesting
I have most of the ones you mentioned, and am a recent convert to SkyDemon and also think it's fantastic.
I just downloaded Circle to Land as I didnt know about that one.
Others I would recomend are:
Aviation W&B
Takeoffcalc HD
Multiconvert
Though Takeoffcald HD has a iPhone version and for the same aircraft (a PA28-181) I got different take off distance results! I emailed the developer and he said some bug fixes are coming along. Just shows you have to be cautious when relying to much on the iPad's. For the moment it serves as a rough guide, and I think the iPad HD version was more akin to the POH than the iPhone (non HD) version.
PS The RocketRoute aeroplates app is a front layer to the plain Pooleys iPlate app. I paid for the subscription through RocketRoute but switched to the iPlate instead.