I think it's possible, but it's rare. The HTML5/CSS3 Based App I'm working on right now does feel like a Native App, but it's because it was designed specifically to mitigate some of the "issues" with HTML5/CSS3 Apps. In terms of User Experience, one of the biggest factors is how the App is packaged and distributed. If it is a traditional Web App, then the UX will be heavily impacted while the content is downloaded from the Web. Especially if the connection is slow, and the content is rich. If the App is packaged as a Native App (which is what I'm doing), then most of the content is local, and only dynamic information needs to be downloaded. In this scenario, the UX is much more acceptable since most of the content does not need to be downloaded, it's already there. I'm using PhoneGap to package our App, and we've specifically crafted our API calls to be very light, so the resulting UX does have a Native Feel. But that does not mean that it's the same as Native, and once you get to that point, you'll find there are additional points that need to be addressed (mainly relating to the limitations of whatever javascript engine you use). Another point is the delay when clicking buttons. But the good news is, all these "issues" can be mitigated if you recognize them, and design the product accordingly. Very different approach from designing the Product without taking this into account, and then trying to "fix" it or "band-aid" it after the fact. Design it right from the start, and the differences become less and less apparent. So I guess my answer would be, not yet, but pretty soon!