e.g. having to tell the app things it could just figure out, sloppy focus that requires you to fuss with the UI, having to input a lot of text in small text box that won't resize or spell check it, having to manually click a button to auto-complete, modal dialog boxes that block you from reading important info in another pane, uselessly vague or incorrect error messages for easily correctable problems cause you to waste hours guessing what the real problem is, returns no error message at all, oh you're using the wrong browser, oh to attach a file in your enterprise webmail you need to install Sliverlight, oh the web based wiki plugin for your enterprise document system only works on Windows with IE, oh mobile browsers are not supported, let me slowly redraw the screen a few more times due to some .Net + Areo legacy issue and hang your window manager, supports Kerberos SSO but requires to you enter a password, doesn't let you enter a username or password since it uses Kerberos SSO... etc.