Why and how rackspace cloud review is so important now-a-days?

As I have read about the Rackspace cloud review, so there are some questions in my mind. What apparatus or device we need to use it and if we connect to Cloud Server as well as use different features then the speed of processing should not be too slow as compared to own desktop PCs working? Whether we will not be able to use USB, CD-ROM etc on it? Please give me some satisfactory answers.
