Tried this one out and results are inconclusive.
I'm a 60 priest and in furblog form I let the tank aggro mobs and then proceeded to cast major Dmg and healing. I would gain aggro about 30% of the time.
I tested this in UBRS and I think aggro is lessened a little but as I said I need more testing on this. However the claim that you can mindblast + heal without aggro is completely unfounded.
However, it is an awesome trinket just for the cute factor
And is great because if you change back before the 3mins you know that you've gotten damaged which is not always obvious in raids.