Depends on what you mean by web apps. Yes, you write your apps in javascript, and build your UI in HTML5 and css, but the apps are installed and run natively on the device and there is no 'web' involved. You can also write your own plug-ins in C/C++ which you can call from javascript.
WebOS might be good in that regard, but its supported development model is limited to web apps so far as I know.