Yeah right, because $Request global variable mainly used in S-Control to retreive the value based on the key & Salesforce replaced S-control with visualfroce page and we can not create new S-Control in org and many organization conveting the S-control into visualforce page and Onclick javascript event.
$CurrentPage.Parameters.KEY_NAME : We have to use this global variable in visualfroce page to read the value from URL based on KEY_NAME.
For more information, please search 'Understanding Global Variables' in Help & Training. https://help.salesforce.com/HTViewHelpDoc?id=dev_understanding_global_variables.htm&language=en_US
$CurrentPage.Parameters.KEY_NAME : We have to use this global variable in visualfroce page to read the value from URL based on KEY_NAME.
For more information, please search 'Understanding Global Variables' in Help & Training.
https://help.salesforce.com/HTViewHelpDoc?id=dev_understanding_global_variables.htm&language=en_US
Thanks & Regards,
Ranjeet Singh.