The "add Picasa brand" comment is good.. I wonder why you don't mention that it is free? That would seriously increase the click rate. I like the buttons in general but the grayish gradient ones are awful and will not blend well with most designs, I would prefer colorful variations from the original white ones, while staying simple, of course. I think you should add the logos of your product also (Picasa, Google Pack) next to the slogan, like you do with firefox, it adds to the visual appeal, otherwise it can be a bit bland.