I was lucky enough to win the entire Smooth Infusion collection from Aveda a couple of months ago, and i've been sitting on them for a while to see what i thought of them.
Naturally Straight Styling Creme-progressively straightens curls with every use
Style-prep Smoother-makes styling faster, easier
Glossing Straightener-All day straightness and shine
These all leave your hair feeling lovely and soft, and they smell the same as the shampoo/conditioner. However i can't really tell the difference between the 3, they all contain pretty much the same ingredients and you use them the same way (apply to damp hair and style/blow dry), however someone more hair savvy then me could probably tell you more.
All in all these are beautiful products. If i were buying them i would buy the shampoo and conditioner, and pick the styling product that suited me best, but i definitely recommend trying them out (or any of the Aveda range, they are all amazing).
Available from Aveda or any good Aveda stockist