The only long term effect I've heard of that appears to be valid is the hit the oyster beds have taken. Apparently, there aren't as many young oysters and that would translate into higher prices over the next couple of years.
It seems someone claims the well is leaking again every month or so, but always turns out false. Occasionally a very small oil sheen will be spotted somewhere along the coast and it's always blamed on that well first, Then tests will reveal it's not from there and it's forgotton.
Every dead animal that washes up on a beach anywhere on the gulf coast is blamed on the leak. It could have propeller cuts and 5 hooks in its mouth but still killed by BP in some people's minds.
From what I've seen, BP is doing what is required of them. They pay for lost business that is legitimate and a lot that isn't. As things return to normal, they are scrutnizing those claims more. My brother in law is from Jean Lafitte, a small town of mostly shrimpers and fishermen. He told me he was disgusted by the apparent greed of the local politicians there shortly after the storm. They and their families were employed by BP for various do nothing jobs such as delivering cokes to BP workers stationed on boats in the bayous down to Grande Isle for $1500 or more a day each. Their boats mostly stayed tied up at the dock. There is still some people who see it as a cash bonanza and are looking for ways to get a piece. The people worst hit are getting help but in some cases, past financial reporting is hurting some. For example, a shrimper will file a claim with BP that his buisiness is off by 50% or totally gone for a few months. BP says OK, show us your receipts and previous years records and we'll pay based on those. They may even pay a little over that. The problem is that the records will not include the shrimp that were sold for cash and not reported. So the shrimper is saying hey, I lost $100k but his receipts and records only indicate $50k. He's angry but can't prove he was due anything more. Some aren't dishonest and just keep poor records. They will likely suffer due to that.
As far as I know, there aren't any major long term effects. By major, I mean something like oyster beds gone or ruined for 25 years, etc. The environment has been and will continue to bounce back. There's no evidence of oil out there now. There was a lot of talk about the oil destroying the salt marsh grasses and escalating the coastal erosion which is a serious long term issue, but that has been quiet lately too. I suspect it isn't as bad as claimed by the alarmists.
The worst long term problem is the way the government handled new permits and drilling afterwards. The moratorium was struck down but the O'bama administration used its influence to keep a defacto moratorium in place. Louisiana was not feeling the pinch of the recession as much as other areas due to the oil industry being such a big part of the local economy. Lots of people lost their jobs because of this and rigs sit unused in port or moved away to other areas. I've been told that the skilled workers have moved with the rigs and when things are allowed to proceed, there will probably be a shortage of workers. The useless policies of government have stifled a thriving business and have contributed to the high cost of gasoline.