NY Times debate: Is Ryan budget viable policy, or just a political gesture?

The Ryan budget is the subject of an online discussion in the NY Times's "Room for Debate" series. Here's how the Times introduces it:

Representative Paul Ryan’s budget may have as many opponents on the right as on the left. One set of critics sees the proposal as “Robin Hood in reverse,” a way to cut millionaires’ taxes and “take health insurance away from tens of millions of people, while effectively eliminating the federal government except for entitlements and defense spending.” 

The other group faulting the plan considers it weak and vague, an election-year promise to cut taxes and increase defense spending, without a concrete idea of how to do this while lowering the deficit. Is the House Republicans’ budget a viable policy proposal? Or just a political gesture?

Read the discussion among five debaters  here.