I'm mixed on this one. On the one hand, GM has had lots of time to get its act together and become a viable company, and has failed to do so. OTOH, they've been doing a reasonable job lately: many of their new models have been very well received (CTS, Malibu, G8, etc.). And Rick only deserves part of the blame for their current situation: everyone is hurting. I'm not familiar enough with GM to know if those good models are Rick's contribution, so I'll limit my comments to that end.
That said, given GM's history, I think a shake up is a good thing. Bringing in new blood, with a new direction, should help things. Clearly something needs to change at GM: why not start at the top?