ok , i must admit i am amazed how they optimized this game for pc.
i have a "shitty" i5 650 dual core @3,2 GHz , 8 GB RAM , gtx 670 , shitty matrox hdd where i have instlled OS + games + porns.
I thought gta 5 wouldn't run with these specs at medium ....i was wrong.
I spent 20 minutes adjusting graphic options following this guide
http://www.gamersnexus.net/game-bench/1909-gta-v-graphics-optimization-guide and i can play at native res with decent framerate , i see no stuttering , only spare minifreeze in online when driving.
Don't know exact frames but i think they were 45-55 (keep in mind i tuned down most of the performance intensive graph otpions like post fx , grass quality , shader quality and reflection quality , the rest is on high cause i don't care about the nipples hd.
MSAA--->FXAA
Anisotropic 18x