I picked up a close-up filter last week which gives me +3 magnification. I primarily picked it up to compliment the 55-200 lens since you just need to get closer than the 3 foot minimum focusing distances sometimes, and changing lenses for a single macro shot is absurd....unless it's a really good shot I guess!
So, the weather was nice on sunday and flowers were blooming, so I went out and tried to play around with it and get crisp shots. I was finding that the DoF was getting out of hand with it at large apertures, but once I got the hang of bumping my apertures up the pictures came out sharper.
Here's the tech data
I've read a review of a close-up lens that Photoj did on the site with their 55-200, and I have to agree that around 100 mm feels like the sweet spot for it, and if you try and push it to 200mm, the results are often soft and blurry.
All in all though, for 10 bucks, I can't complain and it's a fun tool to have in the bag if you like macro photography and can't afford a dedicated macro lens yet.