plastic made from corn?

While eliminating the need for bags and containers avoids the whole reuse/recycle step in the first place, there are times when we may simply need a disposable bag or packaging material. I keep seeing items made from a corn-based material and thought I'd look into it a bit more. I haven't done a lot of research yet and I am hoping some of you out there are experts. I noticed that the reusable coffee/drink cups at Good Harvest Market are made of this stuff and the disposable bags given out at the Organic Valley store in LaFarge, WI were also made of this. I recently read that companies from Newman's Own to Walmart are using it in their packaging. 

So, from what I can gather here are the pros and cons. Once again, the choices aren't straight forward, but this does appear to me to be an improvement over petroleum-based plastic.

Pros:

1. Biodegradable/compostable. I have read and heard mixed things on this. Some say it would break down in a backyard compost, while others say you need an industrial, super hot compost. I did read that it does not need air to breakdown, would that mean it would biodegrade in a landfill?

2. Not a petroleum based product. I think it is getting pretty clear that we need to move away from this dependance for lots of reasons

3. Is a renewable.

4. It uses less energy and produces less greenhouse gases than the manufacture of plastic

5. It is a US product

Cons:

1. May not be as readily compostable/biodegradable as some say. 

2. Corn uses lots of pesticides, herbicides and petroleum to produce. Read Michael Pollan's "The Omnivore's Dilemma" if you want more info on the "evil's" of corn.

3. Corn is becoming an expensive resource with Bush's new Energy agenda to invest in corn energy. 

4. Doesn't do anything to change our disposable culture

I am curious if others know any more pros and cons and if you know of any other businesses using these products locally