So right on everything. Web apps are often unresponsive and temperamental, only their mother can love them. Mouse responses are idiosyncratic (does it change to a wait-mouse when waiting for the server? almost never). Pages change drastically with a simple button press, instead of fluidly updating. Pages get drawn in pieces so you have to check the status bar or tab to see if they're done yet.

Any of these problems in a game for instance would keep it from releasing - Quality Assurance would never pass it! Yet web apps are given a pass on anything. Why? Because there's no simple way to fix them - the tools are too far from the behavior on-screen. You're not in control of your mouse, or your widget behaviors, or your server responsiveness.