The Regional Plan Association, a New York area advocacy group has done a critique of alternatives (PDF, 120K) offered up to the congestion pricing proposal for Manhattan. Their conclusion is that the two major alternatives would not provide the same benefits:

• License plate restriction schemes (i.e., you can’t drive in the city on the 2nd, 12th and 22nd of the month if your plate ends in a ‘2’) don’t provide the same reduction in auto use (many households can avoid this by having multiple cars – some might even buy another car, or individuals who only drive into the city occasionally will just shift their trips to different days).
• More draconian truck restrictions would have very negative impacts on the economy.

But at the same time the congestion pricing plan seems to be having trouble getting traction in the New York state legislature.