Hybrid sales are growing far faster than the overall US car market.
Through March: in January hybrids sales in the US grew +11% year-over-year, February +55%, March +40%, April +55%.
Some models are doing very well. In April Toyota's hybrid sales grew +125% year over year, driven by the Prius family.
Some models aren't selling enough to bother. Lexus (all hybrid models) is only selling about 2,000 units/month.
Some are still too early to say. Chevy Volt got up to 1,700/month, about the same as the plug-in Prius by the way.
Diesel passenger car sales are up strongly too, about as much as hybrids in year-over-year growth rate. But there are still 3 hybrids sold for 1 diesel. I'm not sure why, but the US consumer isn't getting behind diesels yet. Well, even hybrids are only 3% to 4% of the car market. On the positive side, there is a lot of room for US auto fuel consumption to decline.
Here's data
April 2012 Sales Dashboard of Hybrid, Diesel and Electric cars « Elon Musk Founder of Tesla