Rookies,
My daughter Bridie has a Tamron 90mm - it is sharp and gives very nice contrasty images. The AF/MF mechanism is simple to use and I think it was great value for money for a non dedicated macro shooter.
The only downside, if you can call it that is the slower AF than maybe the canon - I don't know for sure as I have never shot with the canon. The AF is fast enough for birds in flight (well seagull at the seaside), but in macro that doesn't matter so much.
Hope this is of some help
Rob