As a longtime desktop developer looking at doing our first large-scale web application, what are the pros and cons of doing web development?

Is developing a web application much worse than developing a desktop app? E.g., is it more tedious or annoying? Is the time to market much worse? Is the web platform excessively limiting? If the answer to any of these is yes, then why?

(And how does developing a Flash or Silverlight app compare?)