GM really needs to revamp itself if it wants new customers (or just stay alive). Perhaps GM's biggest problem is its outrageous bureaucracy, which slows it down and ruins its competitiveness. Its other problems, like those with design and management, are too numerous to mention here, but I think they could really benefit from following the example of how Jack Welch revamped GE in the '80s.
On the issue of branding, I think that GM should kill all their brands but Chevrolet, GMC Trucks, Cadillac, and a new brand name to replace the Saturn line. Buick, Pontiac, Olds... buh bye! The new Saturn replacement line should focus on the youth market and set itself up as the "Honda-killer." A new generation is coming, and GM needs to place itself in a position to capture that young blood. Chevrolet should pattern itself after Toyota and sell the mid-level with a good variety of competitive cars and trucks. GMC and Cadillac should continue as they are, but Cadillac really needs to pay more attention to just what it is that is creating so much success for their competitors.