I've looked for a decent widely-compatible DatePicker alternative, and have not been successful. The Kendo DatePicker is a very nice implementation (it works all the way back to IE8) of the one self-contained widget that I'd really prefer not to hand-roll.

As for other Kendo UI components, I've found the ComboBox, DropDownList, NumericTextBox, and MaskedTextBox somewhat useful, in that they set up quickly and look nice. My typical approach is to use Bootstrap for whatever it has built in, and then Kendo UI with the Bootstrap theme for some extra widgets. Watch out though since they use different box models: http://docs.telerik.com/kendo-ui/using-kendo-with-twitter-bo....

I don't recommend using the Grid for anything but quick-and-dirty development, since any customization is almost inevitably going to be way less enjoyable than maintaining a hand-rolled solution (although the hand-rolled solution will probably take a lot longer to implement at first). The Scheduler is kinda nice but I have the same reservations about it. And don't get me started on the MVVM implementation.

But the good news is that all the basic form input controls (including the DatePicker) are Apache licensed! Until there are more stable and compatible widgets built with React I'll be using them fairly often: https://github.com/telerik/kendo-ui-core

Also, here's the script I use to wrap Kendo widgets in React components: https://github.com/guscost/kendo-react-wrappers

Disclaimer: the last time I used Telerik components was in ASP.net 2.0 about 9 years ago.

For React: http://material-ui.com/#/

Bourbon + Refills: http://refills.bourbon.io/

Material Design Lite: http://www.getmdl.io/

Bootstrap: http://getbootstrap.com/

etc, etc. Even back when I used telerik components, it was often faster to develop my own component, tailored to use-case, than it was to figure out how the hell to customize the 15-deep DOM tree that a table component generated.