There isn’t a blanket yes-or-no answer. Based on the experiences shared, autofocus issues can still happen with some Sigma lenses on some Canon bodies, but it’s not universal. One user reported severe front-focus with a Sigma on a Canon 60D, while another said their Sigma was the most accurate lens they owned. In other words, compatibility and calibration seem to vary by lens-body combination rather than by brand alone.

If a Sigma lens is under warranty and shows a focus problem, Sigma may be able to recalibrate or update it. Since your 500D doesn’t have AF microadjustment, you have less room to correct small focus errors yourself, so testing matters more.

Practical advice: try the exact lens on your camera before buying if possible, or buy from a seller with a good return policy. Don’t assume that all older reports mean the lens will misfocus, but also don’t assume newer production guarantees perfect AF.