I can't say for sure. I made changes in the morning, then didn't check back until the afternoon. They didn't happen instantly, but it did happen somewhere in that time frame. I can tolerate a reasonable delay. I don't update my contacts enough to ever have it become an issue for me. The e-mail timing is flawless, so that's what keeps me happy. I hope they add the sync feature for the calendar.
If you haven't noticed the sync changes by now, something probably isn't right. I would try removing your e-mail accounts from your device, maybe even do a battery pull for good measure. Then re-add them, and make sure the contact sync box is checked. You may find that it will duplicate some of your entries, but from my experience at least, once you clean it up, it's good to go.