Macro Tubes work but they also narrow the depth of field thus making it more difficult to shoot perfectly sharp pics. Not saying that you can't get sharp images w/ extension tubes but you only get super narrow D.O.F
If you're unfamiliar with D.O.F imagine you take a pic of a blenny that's perched up staring right at you, you focus on the eyes and snap the photo, when you study the photo later you will find that only the eyes are sharp while everything just behind or infront of the eyes is completely blurred, sometimes this will appear as a very creative effect adding depth & dimension to the image, others it simply looks like there is too much blur. In comparison a proper Macro lens will have a wider D.O.F.
Give it a shot, for the low price it's definitely worth playing w/ extension tubes
Have extension tubes as well, hard to play with and very sensitive. Manual mode, small window to adjust and get best clarity with the photo your trying to take. You do have to get up REAL close to get a good shot