Good points. However, I have a personal experience with E85 I would like to share.
A few years ago when E85 was first being offered in my area, I took a shot at using it in my 87 Fiero. Before I did, I pulled my tank and installed a new Walbro pump and inspected everything. Basically my Fiero's fuel system used the same type of materials your 87 Buick GN's use (mild steel, rubber, etc).
I ran straight E85 for about the entire summer. Car ran great and the Turbo 3800 loved it. At the end of the season, I pulled my tank to inspect the inside. What I found was the sending unit (fuel lines that go down to the fuel pump and the bottom of the tank) was turning black in color. It appeared to be some kind of corrosion. The metal collar that was on my walbro pump was starting to turn white (corroding), and the rubber fuel line that I got with the walbro to attach it to my sending unit had swelled to about twice its normal size.
The rubber fuel line issue could possibly be explained by what I read on the net about some manufacturers not including approved in-tank-use rubber fuel line with their fuel pump kits. I had seen this swelling up problem happen in other non-E85 situations so I could explain that away. However, what I could not explain was the corrsion buildup on my sending unit's metal parts or the metal collar on the walbro pump. I noticed some of the black "corrosion" material must have come off the sending unit because I saw very small particles of it laying in the bottom of my tank.
Now my tank has a plastic baffle in it that did not appear to be affected by the use of E85. Nor did the metal inside of the tank which appeared to have some kind of coating on it that the sending unit did not have.
Now the question I have is: Does the E85 we get at the gas pump today have better corrosion inhibitors in it than what I used just a few years ago that will stop these problems I experienced?