I have logged, literally, thousands of hours in Kaseya. As stated above, I can do more in the VSA than if I'm in front of the PC. Hugely powerful. People ask me "So what kind of things have you done with Kaseya besides just remote into a desktop"? Then I give them a simple example, such as how I wrote a small agent procedure that allowed me to uninstall Office 2010, install Office 2013, and activate the product with a license key on more than 350 endpoints with (literally) three mouse clicks. And I did it with a 100% silent uninstall/install while the user was logged in and working. They had no idea anything was even happening with their workstation. Kaseya makes what could otherwise be a huge project super easy stuff. Kaseya is probably the most important force multiplier in my environment.
Identifying a con is tough. The only drawback I would point out is that for brand new users there can be quite a bit of learning curve when you delve into the really powerful features. For example, writing complex agent procedures takes experience. That being said, the initial basic use of the most common features is easy to pick up right away, so even the learning curve isn't a big deal. When you're ready to "do more" and invest the additional time to learn the more advanced features, they're there waiting for you. For basic help desk folks, they may never need to go beyond the surface features.
Our workforces is increasingly mobile and regularly have a huge number of endpoints not sitting directly on the LAN. The ability to continue managing them fairly effectively is excellent.