Well, I had only the Miller High Life. I must have missed the Guinness part.
It did not taste as bland as I would have expected it. Given the fact that it has an FG of ~1.007 it is one of the less watery Bud-like beers. Yet it was still a strange taste, that I didn't care for that much. What makes it taste so much different from a good light lager? Is it the 6-row, the rice or even corn?
I'd guess it's the 6-row that they are using. So far I haven't used it myself (and are not planning to do so).
Kai