With regard to UX, web development is a pain in the ass. It's 1000x easier to create a smooth and well developed UX on the desktop than it is on the web.
I believe the web will eventually replace the desktop all together but that's not until it has better access to hardware, especially the GPU.
The frustrating bit is how slowly progress in this arena has developed. 10 years later we're still having the rich vs reach argument.. Why can't we have both already?
The answer is better browser-independent (as far as that's possible) libraries, I think. jQuery and Cappuccino are definitely steps in the right direction.
While I think JQuery is an impressive library, I think it is light to replace a full desktop UI programming model. As well Cappuccino favors the developer over the designer, in saying that their Atlas tool goes along way to remedy that. Currently, (my personal opinion) I think Dojo and to some extent YUI have the most robust libraries to replace the desktop UI development model.
I believe the web will eventually replace the desktop all together but that's not until it has better access to hardware, especially the GPU.
The frustrating bit is how slowly progress in this arena has developed. 10 years later we're still having the rich vs reach argument.. Why can't we have both already?