I verified that Kies Mini does NOT work with the Captivate, at least the latest version does not - it operates as the full Kies does. First, in contrast to the what the wiki currently says, it will say 'Can not connect in debugging mode' if you turn debugging mode on. Second, it will never identify your Captivate as supported in Kies (MTP) mode.
I am updating the wiki. You guys can revert it, but I verified this, and unless you run your own tests I suggest it not be contradicted. If your results do differ from mine, then please do contradict me.
UPDATE: Apparently I can't update the wiki (or didn't see a way) and am not spending all day on this. Do note this inaccuracy though. Note that I didn't try the older version, I let Kies update itself, so ... Maybe you could tell people not to update Kies mini, but what are the repercussions of that? I assume this change was made for a good reason.