Guys at Google know the importance of time and this is probably the reason why these people invest a lot of time on speeding web applications. In case some of you are involved in setup work then you must have realized that the web could have been faster than what it is now.

With AJAX Libraries API Google attempts to make Web applications faster for developers and if we think from the viewpoint of developers then they wont face problems regarding getting caching setup correctly, saving on the bandwidth and network of users and in case some other application is using the same library then there is a slim chance that it would be caching on machine of the user. So if performance is your key criteria then you need to work out with AJAX Libraries API.