On the note of how awful it is to program these panels, even if you are using Compass, it's a massive pain to install, there's annoying inconsistencies between panels, and support, as expected of Honeywell, is beyond awful.
Compared to other low voltage systems these (and some access controllers) are expected to last a decade or more and usually do. In a commercial environment these will see 2 or 3 generations of computers, maybe 2 HVAC and 3 lighting platforms come and go and will still code+away and you're good. Ademco's reach is vast.
The lack of integrations to non Honeywell access control systems is a major weakness as you pointed out. Are there any Honeywell representatives that could respond on whether or not this is something they are looking to change in the future? A follow up question is - has anyone successfully integrated these panels into any third party access control systems?
The Honeywell/ADEMCO panels are some of the easiest to program. Heck back in the day when others systems still have just led lights programming was next to impossible. The Vista 15P is their basic panel they have been selling for years and not designed for the integration that is done now right out of the box. The Vista21IP is the way to go since it has network built in. I grew up on these panels and hated when I had a service call on some of the other panels. DSC was the worst with their tiny screw terminal points.