If you read through the threads on the app page it answers all these questions.

To add a new app all you have to do is unzip and add to the Appletribon folder. Then add the app

Not all apps give u the option to change to F. To change the weather to Fahrenheit it usually involves changing a 0 to a 1 or vice versa in the html code. Restart PointUI and bam...F

Some apps are still in their beta and have bugs. From what I understand its not easy to code for PointUI or the developers aren't that great.

There's a thread for PointUI info and good app recommendations: http://forum.ppcgeeks.com/showthread.php?t=70108