I shoot quite a lot of film and macro is definitely one thing I'd keep using digital for. Focussing is too critical and you have no instant feedback to do any corrections.
Having said that, the EOS 3 is supposed to be a nice body and since you already have Canon lenses, then you are all set to give film a go. It's a lot of fun and, as people above said, if you don't like it, then you can sell the body at little loss. One bit of advice - spend a couple of extra quid on a roll of Ektar (snappy snaps sell this at an ok price if you want to ust get it on the high street) or Portra to really see what people like about film, then you can decide. And don't go mad getting a home dev kit straight away; run a few films through first and see whether the bug gets you.
By the way - there's a film sub-forum here, and if you do some standard searches you'll find loads of hints and tips for someone new to film.