-expensive for developers eg: No knowledge of user's
environment.
-!Cross platform
-No Data sync across machines
Now, before some wise guy says that all n things can be solved w/ n different plugins, let me just say this list is for the general case. Since most people don't have those plugins it's silly to build a business around them. Unless of course you have some way of spreading them, which you usually don't.
It's about the sweet-spot. A professional photographer uses Photoshop in a manner that doesn't work well as a web app. However, a party goer takes snaps and posts them to their web space of choice. Same core concept, different level of use and thus different environment. The platform choice is based upon the target audience. There's plenty of room for both approaches.
Similar dichotomy exists in most spaces, casual word processing works well over the web, but I'd rather write a thesis with a desktop hosted word processor. Ditto for IDE's, CAD, NLE, spreadsheets, etc.
Good:
-Drag and drop eg: Easier to attach a photo to an email
-OS integration eg: iPhoto => set as desktop, Excel => uses outlook contacts
-Access to hardware eg: GPU, usb, accelerometers, camera
-GUI responsiveness
-Fully customizable flow eg: Not forced into the "back" button paradigm.
-Control over version eg: If there is a bug, you can wait to upgrade.
-Control over data eg: I can't get my FB contacts
-No need to upload data to another app to edit it. eg: photos etc
-SPEED
-Works w/o connection
-Keyboard shortcuts
-Richness of GUI
-file assoc - mailto link etc. You determine what app uses what extension.
Bad:
-Installer eg: no "insta-play"
-Spyware
-Manual updates
-no HUGE data sets eg: youtube / wikipedia
-Uninstaller eg: doesn't uninstall potentially corrupt prefs
-expensive for developers eg: No knowledge of user's environment.
-!Cross platform
-No Data sync across machines
Now, before some wise guy says that all n things can be solved w/ n different plugins, let me just say this list is for the general case. Since most people don't have those plugins it's silly to build a business around them. Unless of course you have some way of spreading them, which you usually don't.