Both Square I and Triangle II work fine on my 64-bit system (well, as much as I've tried them so far).
It's nice to have all the synths, even if only to see the evolution they went through from the likes of PSYN to Rapture.
It's my understanding that SFZ+, contrary to its name (and namesake SFZ), won't read sfz files (multisamples), only sound fonts (I know nothing about sound fonts).