A few nuggets on ethanol based on my industry experience with it:
1) Not all ethanol is the same. Sugar cane based ethanol is much more efficient to produce than corn based ethanol. Brazil uses about 85% ethanol in their vehicles (sugar based) and has been very successful at converting their system to ethanol over the last 25 years. Cellulosic corn based ethanol is where the technology is heading and should replace the current thermally derived ethanol over the next ten years improving net-cycle efficiency from about 15% (85% of a current gallon of ethanol is wasted in production, 15% arrives at the consumer) to about 70%. Even thermally produced corn ethanol is not "negative" in it's energy value/carbon footprint, it's just not very beneficial due to the massive thermal requirements in fermentation.
2) Ethanol is not starving anyone anywhere, corn subsidies are. Farmers in the U.S. are paid not to grow corn to keep the price artificially inflated. Ethanol further drives prices up, yes, but if ethanol weren't there those farmers would not be growing corn for export in the absence of ethanol, this is a fallacy perpetrated by the livestock industry since they want/need cheap feedstock for their animals.
3) The worst environmental effects of corn based ethanol are due to the fact that corn is a very destructive crop. It has a very poor root system leading to increased erosion, it strips massive amounts of nitrogen from the soil, requiring significantly higher fertilization rates and nitrogen run-off into our river water systems, which leads to increased bacterial and algal growth and BOD in surface water systems, decreased aquatic diversity, etc.
4) Ethanol "must" be used as an oxygenator in fuels sold in the 26 NOx SIP Call states east of the Mississippi and all NOx non-attainment zones in the U.S. because EPA outlawed the use of MTBE for this purpose in 2006. MTBE was banned as an additive because it was found to have catastrophic effects on ground water if it leaked from underground storage tanks, which occurred with alarming frequency. The only alternative to ethanol at this point would be to require massive catalytic converters on cars to ensure complete combustion of VOC's along with some form of ammonia or urea based injection to control formation of NOx. These would obviously add significant cost to new vehicles.
5) Your mileage will decrease when using ethanol due to the lower calorific value of ethanol on a volumetric basis relative to gasoline. This is also why diesel is inherently more efficient than gasoline...there are more BTU's in a gallon (think skim milk as ethanol, vs. 2% as gasoline, vs. whole milk as diesel).
IMNSHO there is a place for plant derived ethanol based fuels, but they will never be a real solution to offset petroleum based fuels...you would have to plant the entire planet 5X over with feedstock to make enough fuel to support current energy demand.