Over the course of months/years, various security exploits and other issues are discovered and patched in AIR, often requiring you to rebuild and resubmit mobile apps to the various storefronts. This happens often enough that it's worth mentioning as a major con.
While development on Adobe AIR seems to be fairly constant, there is very little communication between the community and Adobe regarding the future and general support of AIR. The track record of Flash (and particularly Flash Mobile) does not inspire much confidence that Adobe intends to support Flash/AIR for years to come.
Adobe AIR does not seem to perform as well (in terms of raw performance, memory usage, framerates, responsiveness, etc.) as other hybrid solutions for certain tasks. For example using shaders tends to be experimental still, and graphic/animation intensive projects often require the use of third party frameworks such as Starling.
Although Adobe AIR is just an SDK without an actual "UI" it's commonly used within Flash, Flash Builder, or FlashDevelop. Considering the integration with Flash IDE, there are very few tools that can compete with its features.
Originally, Adobe AIR was the only game in town, and its blend of flexibility in platforms it could publish to (PC, Mac, iOS, Android), ease of use, and familiarity made it the clear choice. Now Adobe no longer supports it, and we’ve found the transition to Harmon unworkable for us.
DevExpress Universal controls are much simpler to use, implement and customized as compared to Kendo. Learning curve for telerik is high, though level of customization that can be achieved with telerik exceeds that of DevExpress Universal. Found DevExpress Universal community support to be better then its competitors. License cost is also a wining bar here.