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 Rampage III Formula Intel X58, Intel Core i7-930 @ 3.6, Patriot Viper II Sector 7 Edition 12GB, Galaxy Geforce GTX 680 SLI, LITE-ON Internal Blu-ray Burner 12X, Dell UltraSharp U2711 IPS-Panel Black 27" 6ms, Corsair Hydro Series H100, ENERMAX SGALAXY EVO EGX1250EWT, Corsair Obsidian 800D, Windows 7 x64
Alienware X-51, Core firstname.lastname@example.org, 4 gb 1333, 1 TB WD, Evga Geforce 650ti