I've used both SFZ+ and VSTSynthFont. I've had some issues with VSTSynthFont that would shy me away from using it on a gig such as BIAB freezes up. SFZ+ is now free and, I suspect, is a more stable product that VSTSynthFont. I stick with Coyote Forte for most of my gigs.

Here are the links for the two products mentioned:

http://www.cakewalk.com/Products/sfz/
http://www.synthfont.com/VSTSF_news.html

R