The active size of the module increases your zoom some percentage (small, but noticable.).

I wouldn't call 60% extra zoom small. My 75-300mm lens is effectively 120-480mm on my 10D, that is a long lens.

Of course if I had a full frame DSLR with more pixels then cropping down the picture would have a similar effect. In that case my lense probably wouldn't cut it though, with the1.6x crop on the 10D I have the benefit of not using the edges of the len's field of view (which by all accounts are a bit blurry).