I might toss this one by Google, but wondered what you all thought of this... What if I made a little image of one of my comic characters saying how easy it is to organize their photos and saying he's using Picassa to do so-- then the referrel link under it? I wonder if that would fly with the TOS? You're not really tricking anyone into clicking something-- you're encouraging them to try it out for themselves, and they have to go through the motion of downloading and installing it. ???
I did something similar. I didn't use an image. I wrote that I was using Picasa to send my images and I put the Picasa text link below it.
I think what you're doing is fine as you're just reviewing the product. It's not misleading the visitors in any way into clicking, downloading and installing pisaca so I personally see no problems.