Apple told devs that Leopard is RI internally, but not going to ship fully completed until 2008. I turned on RI just now in Leopard and some apps looked great and some did not. iCal mostly looked good. iChat mostly did (some title bar issues). Calculator worked great. Tried a couple third party apps that have RI support for Leopard - they worked great.
So yes RI is in, but its not finished (arg - they had plenty of time) and its not yet really usable. And yes the stuff is vector or high res bitmaps, but zooming does not use the RI stuff.