I just tried this with my India Red Ale back in August, though I couldn't bring myself to let it sit the whole 80 minutes - I went about a half hour. We had one of the two kegs at a party a few weeks ago.
The hop aroma is very nice - like a more refined, rounded dry hopping. The bitterness of the beer seemed higher than what was calculated, and based on my experience with the same hop schedule, so I attribute some of that to the longer steep.
I don't like not being able to get a handle on what the resultant bitterness is going to be - I know I can trial and error it, but I am 3 parts German, and that just drives the precision side of me bonkers.
What I really did not like was the fact that this batch did not drop crystal clear. My IPAs/PAs are usually a touch hazy from dryhopping, but are otherwise clear, and overall all my beers are very, very translucent. This is actually pretty murky. When I tap the other keg, perhaps I'll take a picture of the pint. I suspect that this is a result of not chilling quick enough after the boil was complete?
Obviously, this is only one data point - I would need to do additional trials to see if this is indeed the cause, but the result is not so over the top great or better than flameout+keghopping that I usually do to make it worthwhile, IMO.