NOLA.com has a nice interactive graphic timeline of the BP Blowout. Lots to click on in the sidebar as well.
EPA also released results of its second round of toxicity testing on oil and dispersant and found that the dispersants alone were less toxic than the dispersant-oil mixture. Oil alone was found to be more toxic to mysid shrimp than the eight dispersants when tested alone. Oil alone had similar toxicity to mysid shrimp as the dispersant-oil mixtures, with one dispersant exception. Long-term effects can't be measured this quickly, of course, but EPA tested for endocrine activity and found none, one possible route for long-term effects.
There's been a lot of hoo-ha about dispersant toxicity. I am wary of claims of "toxicity," because often it's not used carefully, as I pointed out the other day. Some of the early hoo-ha was based on the material safety data sheets (MSDSs). I've found that MSDSs always err on the side of caution. And there are lots of things that shouldn't be eaten: furniture polish, cleaning products, even salt by the tablespoonful. MSDSs for them would look pretty scary too.
The dilution of the dispersant-oil mixture is going to be enormous. And bacteria eat the stuff. There will be concern that in eating it, they will use up oxygen, and the Gulf of Mexico already has a dead zone, where bacteria eating fertilizer runoff from the Mississippi River have already used up the oxygen. So far (don't have a link, sorry), from one source that I thought reliable, there is some oxygen depletion from bacterial action on the dispersant-oil mix, but it's not serious.
Letting all the oil go without dispersant would have resulted in more oiled birds, turtles, and shoreline. That wouldn't have been so good either.