Thought I would post some problems that I have had with sigma lenses on my recently bought 300D. I had a 75-300mm 4-5.6 which was great with my film EOS camera but didn't work well with the 300D, the autofocus would hunt forever and kept getting error '01'( the canon manual says clean lens contacts).
I ended up trading in the lens for a Canon 90-300mm as in the shop I tried 2 other sigma lenses, a 28-70mmf2.8 EX and another which I forget what it was but was big and heavy (and expensive too!), but had similar problems with them both. This bemused the shop assistant(for those in the UK it WAS Jessops!) and he couldn't really offer any help so I opted for the Canon lens and would look around for another fast mid range lens( I am INCLUDING the 1.6x image magnification of the 300D here).
Whilst in another shop purchasing a standard Canon 50mm lens I asked to try the 28-70mm sigma on my 300D and got the same problems, another shop assistant in the store, (Jacobs this time) said that he had a D60 with a problem with an old sigma lens, he suggested the Tokina 28-70mmf2.8 ATX.
I bought it and have no problems with it.
Has anyone who uses a 300D had similar issues ?