Whole food blended up is whole food to me.
I regularly substitute meals with a shake blended from protein, banana, oats, peanut butter, etc.
I have not seen any ill effects but then again, I'm not trying to compete.
I eat at least 3 whole eggs per day, the macro nutrient does not change if you chug them vs. scrambled or hard boiled.
As far as changing the GI of oats - blended vs. regular, well, I've seen responses (and studies) all over the place from that one.
Common sense says yes, the GI will change because it's a finer grain when blended. If anyone else can comment on this it'd be appreciated.
Obviously a finer grain from oats is a helluva lot better than most carbs you can get.