At the end of the day, the question is "How well were you able to support your clients?" Once the post-"K2" kinks were worked out, the Kaseya product has helped us do our jobs very well. Remote control, patch management, scripting & automating fixes, monitoring... this is the "cosmic background radiation" of running an MSP business. Kaseya doesn't get in our way, it just gets things done. When we want it to do more, we find ways to make it do more (scripting, monitoring, etc). On the other hand, support goes through some rough patches; every so often we hear about a "renewed commitment" to providing product support, which improves things for a while... and then things go back to "normal." We don't have to open many tickets nowadays, unlike in years past, so this isn't a showstopper. (Just... annoying sometimes.)
The Kaseya platform has come a long way! We really appreciate is complete customization and flexibility. Not only is Kaseya one of the best MSP options out there, it is extremely useful as an in house help desk.
We use it for the Help Desk and Project Tracking as the primary tools, but it is also our centralized patched tool, scripting, remote desktop management, and auditing.
I've been using Kaseya for approximately 5 years and it is by far the best and most mature RMM tool on the market. They have had their occassional issues with new product releases but that is to be expected with any large software platform. The key to Kaseya is its fully integrated nature. It's not just a bunch of bolt on products but is truly one platform. I have been able to grow my business without having to add head count and my techs love it. I have evaluated all the products, including some of the new ones and they don't compare.