The G8 used to be criticized as an evil capitalist group of powerful countries that determines world politics and economics without legitimacy like the UN. There has not been much of such criticism at this year's summit in Japan.
This time, lack of effectiveness was the most common criticism. The G8 is increasingly seen as a Western talking shop that is doing photo-ops with rock stars and third world leaders, but fails to act on its past promises on development aid and is increasingly incapable to shape international economic affairs. 
Besides, Senators McCain and Obama recently had a dispute as to whether Russia should be excluded from the Group of Eight.
Consequently, there have been several reform proposals to make the G8 more effective:
L20: upgrade the existing G20
G13: G8 + the "outreach 5"
G9: leading market democracies
G3: US, EU & China
G3: US, EU & Japan
The Atlantic Community explains these proposals and asks: "Should the G8 be enlarged to include new major international players or contracted to ensure effectiveness?" If you register on Atlantic Community, then you can vote on the above options.
Closer cooperation between Pakistan and Afghanistan is a key factor in enhancing stability in Afghanistan. Therefore the G8 are launching "a coordinated package of measures ranging from assistance for refugees and returnees to strengthening parliamentary contacts. Since a particular focus of the package is support for local security services and border protection, much of the funding is to be spent in the Afghan-Pakistan border area." The press release from Germany's Federal Foreign Office does not have much more information unfortunately.
The G8 plan is called "ambitious," but I wonder how serious the plan is since the press release states that Germany will only make 9 million euro available for 2008. Or perhaps it's more important how the money is spent rather than how much is spent; see Kyle's post about criticism from Congress regarding aid to Pakistan or the essay from spring 2007 "When $10 Billion Is Not Enough: Rethinking U.S. Strategy toward Pakistan" by Craig Cohen and Derek Chollet in The Washington Quarterly (pdf). Still, I believe 9 million euro does not go very far, even if the other G8 countries pitch in as well.
And with this, Germany's G8 Presidency ends. Japan will take over in 2008. Germany was not very successful, I believe. See the following Atlantic Review post: Who's Right on the G8-Summit: Bloggers or Academics and Politicians?
Related post on Afghanistan: Fixing the Afghanistan mission: The U.S. wants to try, but what about Europe?