As I said, a lot of people don't know about them. ;) PDQ Deploy is a remarkably affordable software deployment tool, they charge by the admin using it, not by the PCs covered by it, and the yearly cost gets them automatically building for you... most of the deployment packages for common Windows software IT environments deploy. I've never used PDQ Inventory, but it ties in pretty closely with Deploy if you use it as your auditing and asset management tool.
PRTG is in the vein of Nagios and WhatsUpGold, but far more delightful to use.
I wouldn't call either specialized, except perhaps in terms of organization size. If you're in Fortune 500s, probably not going to end up with these tools.
I’m not saying that they’re not great at what they do for their segment, but I do think they’re more specialized.