I have a 30D and my wife wanted a DSLR for her anniversary.  I have a collection of nice Canon lenses, including this one.  When she got her Rebel, this was the lens she ended up stealing from me.  She uses it 99% of the time.  On the Rebel, it makes for a fairly small package and exceptional pictures.  The focus speed is fast, and the image quality is comparable to L-series zoom lenses.The only real downside is having to use your feet to zoom in closer to an object. 

Question: How is the image quality?
Answer: the image quality is comparable to L series zoom lenses