7 days JR Pass price is almost same as round trip fare between Tokyo and Osaka by Shinkansen. That means if you have one way trip from Tokyo to Osaka or reverse, JR Pass is not worthwhile using. However if you add some trips when you stay in Osaka and Tokyo, you may use JR pass 7 days.
Japan Rail Pass (a.k.a. JR Pass) covers all JR lines throughout Japan. This is only rail pass that covers throughout Japan. If you travel even round trip to Osaka from Tokyo, price of 7 days pass almost equal to normal fare. I think this pass gives the greatest deal to the travellers who wants to travel in Japan.