Glide is officially a dead api; 3dfx is not going down that road anymore in the future. Does UT play better under glide than d3d? Yes. But the new 4.20 patch came out yesterday so I haven't tried the d3d code yet.
I would return it; the geforce is a better all-around card than the v3.
Asus P9X79-Deluxe, Intel i7 3930k @ 4.2Ghz, 16gb DDR3-1600 Kingston HyperX Memory, Coolermaster Storm Trooper case, Corsair AX850 psu, Geforce 680 SLI, Corsair Model H100 w/c, Samsung 840 Pro 512gB SSD, Asus Blu-ray Writer 12x, Windows7 Pro x64