This sort of "web applications" make me question the value of the Google's "web app store": so far the only true web application from the store I've seen, were Angry Birds. The rest I tried were either Flash applets, or, in this case, require some "Roozz plug-in" (which I wouldn't install). What's the value added by Google here? Only to tell me that I need Google Chrome, because my IE9 is "not supported by the web store just yet", and use Chrome to play Flash or launch installation of some weird plugin (which, by the way, doesn't seem to have problems with me using IE9)? Will such "web apps" even work in their own Chrome OS?
What's even more puzzling is why LinqPad needs all that? Downloading setup package from their own website is much more straightforward way that 1) doesn't discriminate people by browsers they use; 2) doesn't require any 3rd-party plug-ins which most of the people are grown to be wary of.