Canon EF 100/2.8 Macro
The shortest opinion possible: excellent lens; if it only had the USM drive! Not long ago Canon finally made the USM version; why did they wait for so long, I have no idea. Maybe they simply assumed that macro-photographers don't care about AF anyway as most of the work is done in manual mode? Maybe. Still, for the lens as expensive as this one, it would be nice to have the USM drive as a bonus. Even if it is a MACRO lens, you CAN use it for other purposes too.
Those more interested and capable to read Polish may want to dig through 1998 FOTO for my article "Kupujemy obiektyw do makrofotografii – Canon EF 2,8/100 mm Macro", Foto 5/98. For those waiting for a quick advice: buy one (I mean the lens, not my article)! If you are into macro photography, you will love it. It is sharp as a razor, the front lens is well hidden deep in the casing, so that you will not ever need to use any sun shade, the front accommodates Canon macro flashes, making the whole set quite portable and convenient to use. In professional tests of optical quality, the EF 2,8/100 mm Macro is permanently one of the best macro lenses on the market. In comparison to its competitors, such as Nikon, Minolta or Leica it also tends to be slightly less expensive. There are, of course, some cheaper macro lenses on the market too, but with those you substantially loose on quality. If money is not the most important matter, go for the new USM version - the old AF motor is, honestly saying, somewhat annoying when it tries to seek for a focus without much success but making loud whistling sound.