I can see where Jane Hamsher’s tea-party/populist left united front thing could seem appealing as a movement against something (the no-good politicians in Congress and their corporate special-interest shenanigans).
But I can’t see how it could be a movement for anything. Progressives want more government, and tea-partiers want less. On a very fundamental level they can’t make those two goal work together. They will only ever be together in what they are against, and even then it’s more of a vague, boogey-man sort of villain. It’s the process, really, that both these groups despise. But their real long-term goals are so far apart that no coalition of any import will ever form between them.