I dunno how much this will improve your macro, dont get me wrong, its great as a "stage" on which to shoot, but generally especially with extention tubes your field of vision will be tiny.
Its not like your shooting a coke can product shot, its much closer than that.
Course you still need backgrounds and as much diffused light as you can get and the thing has a million and one other uses, though I dont think its absolutely necessary for macro.
I read somewhere....it might be here about a macro shooter using half a ping pong ball over his subject, fly or whatever and shooting through a hole in it, that gives you an idea of the scale of the area your actually using.
A ringflash is a great buy for macro...