It has one of the best WebUIs that I have used, because at a glance looks simple, but offers us a lot of options to secure all the traffic that is passing through the device (or all traffic that the user decides to pass through). Besides, the way that scan the applications to detect what kind of application is do not affect anything about the device's performance. The way that the product process or handle the traffic, is one of the best in the industry.
Improvements to My Organization:
Well, I work as a security consultant, so one of my functions is to help and provide to the end users with recommendations about technologies or process to secure their network. So, one of my customer decide to migrate from TMG/UMG to Palo Alto, it took a while, but during this process, I showed them many ways to improve their current security with Palo Alto, and after a while, they are very comfortable with the technology, for them now, it is easier to apply some kind of web filtering or application filtering than the past.
Room for Improvement:
I'd like to see a wizard to create IPSec VPNs. They need to improve the graphics to show the network behavior.
The stability is acceptable.
It depends about the project, but offers a good HA option.
Always show to the customer what the product can do for them and what not, is a good practice, because they can open their eyes and to be sure what are the benefits of that technology. Always analyze the network topology, using the customer's network diagram and ask every doubt that you have, for my experience a good analysis and deployment plan give us a successful implementation.