maybe an other option you might want to consider: Canon macro EF-s 60mm 1:2,8. It's perfect for portaits (on 50D 96mm) It's producing very sharp images. Great for macro on flowers. For insects and other bugs you need to be too close.
I bought mine "used". Apart from lens scratches, there is little what can go wrong with this lens. it's very solid build, and as it does not extend nor rotate the front lens, it does not collect any dust or moisture inside.
And if you like this one
, start saving for the Canon macro EF 100 1:2.8, anything else will disapoint you later on