Im Telerik customer from 2010 and i can say Telerik is company which offer very good products for developers - i speak abou Ajax Telerik, Kendo and Winform. One of product looks like was abandoned -JustCode. But telerik always say no no, we are working on it :). But globaly, Telerik brings very good portfolio at good price.
Bugs. At 2010 i saw WE ARE WORKING ON IT VERY HARD. But same today in 2016. Just make 1 release dedicated to fix all bugs and no new functionality.