A discussion of advances in solar panels is here. The industry needs to get its price down to about $0.52 per watt (cost $0.26) to achieve installed price of under a $1.00/W, (for 13% efficiency Copper Indium Gallium diSelenide / CIGS panels).
Daystar Technology may be reaching $3.00-$3.50/W installed price in 2007 with their Gen II production if everything goes right. They are achieving 20% efficiency in the laboratory. Daystar plans on reducing its installed price to the range of $1.00/W when its Gen III production is tuned up in 2009.
A south African group is getting its cost down to $1.66/watt, which would be about $3-3.50 installed
A comparison of solar cell technology