Of all the many (many, many) lenses that I've owned, borrowed, or rented over the years, this is probably the only one that I really regret selling. It was so incredibly sharp, focused so consistently (despite only being f4), and was such a good price even purchased new, it's difficult to believe.
Until the 70-200 f2.8 IS II came out, this was my go to telephoto zoom, being both sharper and lighter than the original f2.8 IS.
Used mainly for portraits and sports, I will probably end up buying this lens again in the near future.
Some of the shots I took with this lens can be seen here.