Other tools from Telerik are not negatively impacted by Kendo UI. In fact, in the case of MVC, there are benefits. As an example, the work done on Kendo UI charts directly benefited and enabled the new HTML5 charting available for MVC. If you're a Microsoft developer doing traditional server-side development, I'd encourage you to stick with one of those UI solutions from Telerik.
Finally, we clearly disagree that Kendo UI is even slightly hackish.
Kendo UI is being built from the ground-up without cutting any corners to deliver the best performing, most complete jQuery-based HTML5 UI framework. This is not another jQuery UI clone. If you want a jQuery UI clone, they're a dime a dozen and you're welcome to try them. We think we can do better, especially in areas of performance, release schedule, and complete, integrated framework.
Hope that helps. If you have any actual feedback on the beta bits after giving them a try, we'd love to hear that so we can make the first version of Kendo UI as good as possible.