Presumably, it shares the common advantages of any web-app, e.g.
* Always up-to-date
* Always available on any machine (in theory)
* Built-in accessibility (if designed properly)
* Less of a security risk to local machine
Of course, that's not to say there are no disadvantages ...
- requires Internet to work (Internet is not electricity yet, + I'm personally opposed to putting things on-line that don't have any reason to be there)
- you don't control updates (what 'georgemcbay said about VS 6.0 + devops hell when you don't get to control your dependencies)
- current web apps suck at customization (I can't imagine having my Emacs in cloud)
- as the IDE goes to cloud, so does the file system, thus seriously crippling usability (closely tying data to applications is one of the stupidest things that came out of SaaS trend)
When it comes to tools you rely on to do day-to-day development "Always up-to-date" is, at best, a very debatable advantage if looked at from the point of view as the user and not the developer of the tool.
As a for-example, the initial Visual Studio .NET IDE releases were horrible and most people I know who did Windows development in that time-frame stayed on VS6 for quite a long time after it was officially obsolete.
* Always up-to-date * Always available on any machine (in theory) * Built-in accessibility (if designed properly) * Less of a security risk to local machine
Of course, that's not to say there are no disadvantages ...