I've heard of this before, but seeing as I never play Spy (unless I feel I can do it without bringing my team down - I'm one of the world's worst TF2 spies

) I didn't really care enough to wonder about it. Hopefully they do fix it though. Is it time to rally everyone to spam Valve with bug reports? :O
On my computer, certain visual effects don't work (medigun beams, flames, etc.) due to my (non-upgradeable) graphics card, and that must be included because I can never see the aura around the halo even on non-cloaked players. So if you're ever playing against me it won't give you away.

That also means this is the first time I've seen it with my own eyes and not just been told about it.